my xenopus is sick

[bianchina]

Hello!
2 weeks ago, a xenopus laevis of mine got sick, he floated by one side and he was bloated. Then he began losing his superficial skin (however, he was pretty lively). A vet suggested us an antibiotic and she healed. (he is still alone in a own tank, for safety).
I couldn't change all the water in the big tank because it's a 250 l, i changed it partially and i put into the water bioconditioner and antibacteria/antifungal.

This morning i have found another frog upside down. she has both similar and different symptoms from the ones of the other frog.
Similar: it she is losing her superficial skin
different: she is not lively at all, she doesn't move if i take it in my hand, she doesn't float by one side, but she tends to stay by the surface most of the time.

what could it be?
Can i do something? (I've put her in a different tank by herself, she had a salt bath and the antibiotic i used for the other frog)
Should I change all the water in the tank? which parameters should i check in the water?
Thank you very much

[FrogLover2009]

I would try and change all the water in the tank. If you don't it seems like it will happen to everyone soon enough. Change the water, make sure all substrate and special toys/hideouts are clean. Something is causing them to be ill. If you don't want to have to clean it all then put medication in the tank with all the rest of them to see if that helps but changing out all the water would do it. I would recommend checking these websites out as well..

African Clawed Frog Housing and Feeding

Can I keep other aquatic life with my ACF?

African Clawed Frog Disease and Injury

Disease & Illness