Help with a platy which gave birth to frys

[rca.myworld]

I urgently need some help with my favourite platy fish. She is not well. I have posted this to another forum a few weeks back.

Background as of 19 January 2021
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This one had given lots of Frys but seem unwell. First she had a problem with her mouth which seem like mouth rot so I gave her antil fungal from interpret. Now the mouth rot is gone but she is very lethargic and swimming on her head so another platy was after her. I have noticed and she seems a goner but I managed to take her out and give her an aquarium salt bath for 30-45 minutes with disease clear from king fish and plenty of oxygen.
I have checked water parameters and they seems all ok. Ammoni :0 ppm. pH is on a slightly higher at 8 but this has been the case for past 6-7 months. I am planning to bring either peat moss or some almond leaves to naturally lower pH.
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Since 19th January I have given her Anti internal bacteria from interpret (last dose on this saturday) Since saving her with that aquarium salt bath, she eats and swim but mostly in a bit different way. Often times she is in one corner with head up and tail down (completely opposite to how she was before, tail up and head down). She also swim straight up with her head going up and tail like an algae eater.
What I have noticed is that whenever I change water and clean aquarium, afterwards she struggle a bit and goes down on side sometimes or swim on her side etc. What is wrong? Previously this same tank has nitrite problem with nearly 0.25 but now that's gone as well. All other fish seems well in the aquarium and none of the water parameters are out apart from pH which is 8-8.5. Previously I used to put the water in the tank and after filling up the tank dechlorinate it. Since 19th Jan, I have changed this practice and now bring the water to another bucket put Seachem Prime, mix it well and then pour it in after 1-2 days into the tank. The temp is nearly identical to the tank. What else could I check and give her?
Any ideas?

 

[Uberhoust]

I am not really knowledgeable about disease but I am wondering that the elevated Nitrite levels are indicating that the antibacterial medicine has killed off the bacteria that convert the nitrite to nitrate, and the bacterial fauna condition is getting worse with cleaning.

 

[Essjay]

pH is on a slightly higher at 8 but this has been the case for past 6-7 months. I am planning to bring either peat moss or some almond leaves to naturally lower pH.

Platies are hard water fish which prefer a high pH.

What other fish do you have in the tank? If you have only hard water fish, leave the pH alone.

 

[rca.myworld]

I am not really knowledgeable about disease but I am wondering that the elevated Nitrite levels are indicating that the antibacterial medicine has killed off the bacteria that convert the nitrite to nitrate, and the bacterial fauna condition is getting worse with cleaning.

Thanks. I don't know because the tests are coming OK.

Platies are hard water fish which prefer a high pH.

What other fish do you have in the tank? If you have only hard water fish, leave the pH alone.

Hi,
I have 4 platies including this one. 1 guppy male, 1 dino male. 3 frys (old enough to stay with the big ones).
The problem is only with this one.
She still swim a bit different and like I said she has on going problems in the 2nd aquarium.
That aquarium is heavy planted with 2 cardinal tetras, 4 platy frys medium or old enough not to get eaten, 2-3 amano shrimps, at least 9-10 smaller frys (they are very small) from the said platy which is move into the smaller aquarium and is not well. This one is Superfish Home 80.
Both aquariums water is OK. The said platy was first the only one which has mouth rot and fin rot. It is treated at least 2 times for that, 1 time from King fish disease clear. The fin rot is clear now and she is OK but even then she is strugglin with swiming, swim sometimes on her side, mostly go up like Algae eaters with her head up and tail down.
I have given her a salt bath last time at the last resort because at that time she was literally head down and tail up situation. At the very least she is still alive and swimming. The only thing I say is that since I got her from the LFS and she was much smaller she still sit at one corner sometimes. I am not sure if there is long term poisoning because last year June is my first experience with fish tank. I was learning at that time and my observations weren't good enough. I only lost 2-3 fish and that's also within 2-4 months.
Any ideas?