Black Patches On My Guppies Tails?

[Fraoch]

Hi, Ive had my tank for about 4 months now and about a month ago i added 6 female guppies and 2 male guppies to the tank which already had 2 platys and 2 black neon tetras in it. Not long after i added them, my black male dissapeared and when i checked the tank i couldnt find him so i can only assume that he died and the other fish ate him.
About a week or two later my snakeskin female guppy also died 2 days after i found one of her pectorial fins was sticking straight out from her body and was white adn she couldnt move it.A day later she died suddenly.
Then about a week ago i noticed all my platies and guppies were flicking and rubbing themselves on the gravel in the tank. I looked into this and decided to treat them for whitespot a couple of days later.After that they stopped rubbing and flicking and acted normal.

Now 3 of my female guppies tails have turned black at the base and one has streaks on the tip of her tail aswell. 1 of my platys has had some of her scales turn slightly darker aswell. Is this normal for them to change colour now and again? Or is it something to do with the treatmeant i gave them?
This is a picture of one of my yellow females. She has black at the base of her tail and on the bottom tip.View attachment 61418

I also ordered some new fish from an online store a while back and they took some time to get the fish in stock and now should be arriving tomorrow. So now i need to no whether to put the fish in the tank or what to do with them as i dont have another tank?

Sorry for such a long post but i thought you ould like to know the background, and i ahve posted this in the livebeares section also but i really need to know what to do with the arriving fish
thanks fraoch

 

[AstonN24vantage]

a picture would really help

also i would try the emergency section next time.

 

[WILDER]

How many gallons or litres is the tank.
How many fish and which type.
Water stats in ammonia, nitrite, nitrate, and ph.

Need to rule out bad water quality first, as all the symtoms you are describing can point to bad water quality.
Flicking and rubbing.
Blackness to fins can be ammonia burns that are healing.
Any red edging, or red streaking to fins.

 

[Fraoch]

How many gallons or litres is the tank.
How many fish and which type.
Water stats in ammonia, nitrite, nitrate, and ph.

Need to rule out bad water quality first, as all the symtoms you are describing can point to bad water quality.
Flicking and rubbing.
Blackness to fins can be ammonia burns that are healing.
Any red edging, or red streaking to fins.

70 liter tank i have 2 platys, 2 black neons, 5 female guppies and 1 male
I dont have an ammonia tester but nitrite and nitrate are at 0 and ph is 6.8
No other symptoms or anything unusual apart from that

 

[WILDER]

Get your water tested at the lfs and ask them to write the readings down for you.

Water change for now.

We need to check that your ammonia reading is 0.

 

[Fraoch]

Get your water tested at the lfs and ask them to write the readings down for you.

Water change for now.

We need to check that your ammonia reading is 0.

ok, em problem is that my nearest lfs is a 2 hour drive from here and i cant get there anytime soon.

 

[WILDER]

Keep doing water changes for now.
Invest in some liquid test kits.

If there no improvement with the black patches get back to the board.

 

[Fraoch]

Keep doing water changes for now.
Invest in some liquid test kits.

If there no improvement with the black patches get back to the board.

ok thanks so much for the help