Thank you again! I think your advice has worked, or at the very least had a bit of an improvement on the fish. I separated the bully for about two hours, and within the first hour the fish I was most worried about most started swimming around as normal again. He looks much better now, and has stayed that way since putting the bully back into the tank. It has only been a day so I can't say for sure if everything has been solved, but definitely seems to be some improvement. I've started off with cutting back on their food today as well. My fish knowledge is still not exactly up to par (who knew owning fish could be more a difficulty for me than owning dogs and cats?) so I can't say for sure, but I'd like to believe that seeing them all swimming around energetically is better than having one of them moping at the bottom of the tank.
I really hope this means they'll all be alright and live happily now.
