Why is my fish on its side and wiggling?

I have a 38 gallon tank and everything is fine. i have about 11 fish on there. My yellow and black wag platy is on the ground of the tank, on its side breathing. it was also happening to my red wag platy. my yellow platy has cotton on its two fins and dots on its tail so i treated the tank for ich or ick. now he is literally wiggling like a worm on the gravel. my red wag paty has been in the same place for 3 days but he moves once in a while. he's been sad lately and please take this seriously. i feed them enough EVERYDAY but i haven't fed them for three days but everyone was ok. If this helps, i add API stress zyme every week to take care of the nirties and bacteria. the ich or ick medicine is tetra fizz tabs for freshwater fish. i heard it raises the ammonia level but i've used it before and they were ok. I have 2 neon tetras, 9 platies orted and a erfly pleco.