I had a similar situation a while back. The fish was a little thin, maybe not getting enough to eat because of being on the bottom of the pecking order? He didn't really look bloated but I did an Espon Salt dip anyways. 1Tablespoon in a gallon of tank water for 30 minutes. But I stayed with him to observe. That's a LOT of Epson Salt, distress can happen quickly! After 2 days, 1 dip per day, he started to pooped. He was back to eating the next day, so I started him on Metro soaked food for a week. Best guess was the bulling caused stress which caused a bacterial infection.