Ammonia Detector FISH EMERGENCY!!!!! Dropsy/Tuberculosis?

FISH EMERGENCY!!!!! Dropsy/Tuberculosis? - ammonia detector

A couple of days, I bought three red platys for my tank. Died the next day one of them, because he played with the ammonia detector and the pain itself

But today one of them has a terribly swollen belly (I thought she was pregnant in the first place) and protruding scales are really bad. She could not swim around the tank a lot and usually remains in the upper reservoir of heat or deep in the farthest corner. She will not eat.

I was very worried about him and last night I had nightmares of fish and awoke at 3 clock and was able to sleep only at 4.45 clock.

I also have other laminar then 2 litters of juveniles, but had his third night. Is it safe there for them? It is my favorite fish.

I think my tank free on May ... I get a tank of 29 liters in a week, but I have about 11-12 fish in there (clean water) are still very large

And what happened to my fish? What can I do for him?