Red wag platy not eating, damaged pelvic fins
I have a male red wag platy that is normally very active, but has become reclusive since a few days ago and won't eat anything I've given him; I've tried tropical flakes from Aqueon (usually what I feed the platies) and small bits of peas. In addition, the pelvic fins are badly damaged with a bit of blood visible -- there was a great deal of white growth around them this morning that got scattered after he darted away because I bumped into the tank stand by accident.
He usually hides around the bottom or top part of the tank, and backs away whenever I approach the tank. He swims around very slowly now, but that seems to be from lack of eating. There doesn't seem to be any visible bloat compared to the three other fish (all male platies) in the tank. The other platies leave him alone.
They're in a 29-gallon tank with two filters: a hang-on back filter from Aqueon and a Hydro-Sponge filter. I've had the platies for about 10 months, and I change 20% of the water about weekly. There is also a snail and a few plants.
It seems like constipation in combination with fin rot, but how would I treat this? I'm considering doing a Epsom salt bath in a separate bucket with tank water to treat the constipation.