Need help with my Betta!

[Mochii]

My brothers office closed due to covid and I ended up with these beautiful Betta fish on my hands. the first thing I did was move them to a bigger environment , I admit I am still working on it but this red guy is either a really picky eater or I worry that he has fin rot (from what I read). I’m no fish expert and I’d really love some help on figuring out if he’s okay and if not what I can do to help him.

 

[Rhianne]

What’s your water temp and water parameters?
The ideal temp for a betta is 25-27 Celsius. They can survive lower temperatures but it can make them lethargic and they could stop eating.

 

[itiwhetu]

Lots of live plants will help

 

[Rhianne]

Also what are you feeding it?

 

[Mochii]

deal temp for a betta is 25-27 Celsius. They can survive lower temperatures but it can make them l

Also what are you feeding it?

So I have a water heater currently, they're looking happier! I see like a clear membrane forming on their tails which I believe should be their tails growing back. I been back and forth with the food. I'm switching between the KYORN betta pellets and TetraPRO color crisps but they hate the pellets , they spit them right back out so mostly the crisps for them

 

[Mochii]

Lots of live plants will help

I know, I feel bad
Currently moving so this is a temp home for these guys but I plan on getting a 10 gallon setup for them with live plants and water filtering. As of now I'm just changing 25% of water manually every day