My Male Lyertail Molly is Acting Weird

[BakedFish]

I have a male molly living in a 20-gallon with 2 small shrimp, a few small snails, a bristle nose pleco, 3 female mollies (two of which are his daughters), 2 male guppies, 4 baby mollies, and 6 tetras. Around 3 weeks ago I saw him sitting at the bottom of the tank barely moving. The day before he was super active and trying to mate like always. I did a water change and also reduced feeding by 30% in case it was due to overfeeding. I also fed some green peas to all the fish and put some salt in the aquarium. A few days later he wasn't on the floor anymore but now he stays almost always at the top of the fish tank and doesn't even bother to go near the females which he always used to do. There's enough oxygen and I don't think he's eating biofilm. The other fish do not exhibit any of the strange behaviours of the male molly. Could it be an illness? (Re-uploaded but removed the previous thread due to no reply and the wrong thread).

Important Note!
I had 4 female guppies 1 month ago and I think they died of the same thing. First, they started breathing at the top of the tank, then, their tail was floppy, their gills were extended and they were swimming all wobbly. Soon after they stopped eating or ate very little and all their fins were clamped. 3/4 got sucked into a filter and died because their fins were locked.

Info:
Tank is cycled
Fish have been in 20 gal for 4 months but I've had them for 1 year+
Nitrite, Ammonia, and Nitrate levels are all at 0
The GH is 150ppm - 175ppm
HK is 160ppm
Ph is 7.5
Chlorine is 0.
I have an airstone for oxygen
I Feed 2x a day
I also use a filter that goes up to 35 gallons.
The male is around 1.5 - 1.75 years old.
I have 6 natural plants (more coming very soon)
I change the water every 2 weeks 35% (using aquarium temp water or a bit higher)
I clean the decor, filter, and substrate
The week within I do a small 15% but do not clean substrate or decor, only the filter.
I use liquids/supplements like Seachem Prime (not always), Seachem Flourish, and Big Al's water conditioner and bio support.
I have a black sponge filter in addition to the mechanical filter

Additional Question
Why does my female molly do this? She has done this almost since we first got her. She has never been sick and she is currently healthy. She does it a few times per day.

Edit: The Male Molly's tail is beginning to fray and I think it's getting smaller.

 

[Fishfunn]

I use liquids/supplements like Seachem Prime, API stress coat, and Seachem Flourish along with Big Al's water conditioner and Big Al's bio support. I use them every week but put 1/2 - 3/4 of all doses during the week of the 15% water change and the full amount the week of the 35% water change.

• First, you are adding too many additives to your water. Just use Prime to dechlorinize water only. Using API Stress Coat is overkill, plus it adds more stuff that can cause your fish grief. Your fish have a natural slime coat, and adding API stress coat is not needed. If you really need to add Seachem Flourish, do so sparingly. In my established tanks, I never need or use liquid fertilizer. The fish waste has more fertilizer than I need. I only used Flourish root tabs for established rooted plants. Depending on the size of the plant dictates if I use root tabs or not.
• Dont overclean your filters. It takes time for them to recover the valuable nitrification bacteria to keep your fish healthy. I clean my filters only when I notice reduced water flow by getting clogged. When I clean them, I only clean in used aquairum water to rinse the muck out that is causing blockage. I never have to add bottled bacteria to my tanks again once the filters have cycled.
• Make sure when you do a water change, the added water's temperature is at the same tank water temperature or a little higher. Adding cooler water to the tank will temperature shock your fish and cause an Ich breakout.

 

[BakedFish]

• First, you are adding too many additives to your water. Just use Prime to dechlorinize water only. Using API Stress Coat is overkill, plus it adds more stuff that can cause your fish grief. Your fish have a natural slime coat, and adding API stress coat is not needed. If you really need to add Seachem Flourish, do so sparingly. In my established tanks, I never need or use liquid fertilizer. The fish waste has more fertilizer than I need. I only used Flourish root tabs for established rooted plants. Depending on the size of the plant dictates if I use root tabs or not.
• Dont overclean your filters. It takes time for them to recover the valuable nitrification bacteria to keep your fish healthy. I clean my filters only when I notice reduced water flow by getting clogged. When I clean them, I only clean in used aquairum water to rinse the muck out that is causing blockage. I never have to add bottled bacteria to my tanks again once the filters have cycled.
• Make sure when you do a water change, the added water's temperature is at the same tank water temperature or a little higher. Adding cooler water to the tank will temperature shock your fish and cause an Ich breakout.

I Forgot to say but I only use API stress coat if they look like they are behaving abnormally—the rest I use weekly. I will use Prime less often since I only bought it because the nitrate and nitrite levels, in the beginning, were very high (I cycled but poorly and had few plants and a filter too small for the aquarium). Now the water is mostly stabilized. I might still use Flourish but less as I bought it when the centrepiece plant lost almost all its leaves (holes in leaves) and turned a deep green instead of its light green colour. Now it's okay and growing fast. Also, as you said, I do add water that is the same temp as the aquarium or a little higher. Is the fish just acting up because of the additives? It's only one fish acting strange.
When I look at him his skin looks a little "ruffled" or "grainy" (not talking about skin colour/pattern).

 

[emeraldking]

It's probably just stress. Don't use too much supplements too often. Once a tank is balanced, don't add supplements or additives. And you need to know that each individual specimen has got its own margin in tolerance when it comes to fluctuations in the water parameters. So, if we speak about the same type of fish, their tolerance in fluctuations differ. So, one can be very sensitive while the other has got no problems with it.

A male that doesn't chase those females, is not something one should be worried about. I've got a complete healthy sailfin male overhere and he's not chasing those female either. If he's got the urge to chase them, he will. Just let it be...

Yes, what could also be a reason why it's at the surface the whole time, could be illness relatd. But if I look at those vids, he's not gasping for air. But you've metnioned that his skin looks grainy or ruffled... That itself could mean an illness. I would start giving him a salt bath. See if that skin will look normal after such a treatment. In those vids it's hard to tell whether the skin is grainy or not.

 

[BakedFish]

It's probably just stress. Don't use too much supplements too often. Once a tank is balanced, don't add supplements or additives. And you need to know that each individual specimen has got its own margin in tolerance when it comes to fluctuations in the water parameters. So, if we speak about the same type of fish, their tolerance in fluctuations differ. So, one can be very sensitive while the other has got no problems with it.

A male that doesn't chase those females, is not something one should be worried about. I've got a complete healthy sailfin male overhere and he's not chasing those female either. If he's got the urge to chase them, he will. Just let it be...

Yes, what could also be a reason why it's at the surface the whole time, could be illness relatd. But if I look at those vids, he's not gasping for air. But you've metnioned that his skin looks grainy or ruffled... That itself could mean an illness. I would start giving him a salt bath. See if that skin will look normal after such a treatment. In those vids it's hard to tell whether the skin is grainy or not.

Ok, I will start giving him a salt bath, and I'll lower the frequency of supplements/additives. Thanks for the help.