It sounds bacterial to me. Usually if they are bloated due to food/blockage, Epsom will help them pass it within an hour or two.
I have seen fish bloat up due to bacterial infection when all the other tankmates are fine.
I would normally put them down once they developed what looked like raised dropsy scales. They're usually pretty far gone at that point. But you could still try Tom's suggestion of using an antibiotic if you think it may save the fish.
I have seen fish bloat up due to bacterial infection when all the other tankmates are fine.
I would normally put them down once they developed what looked like raised dropsy scales. They're usually pretty far gone at that point. But you could still try Tom's suggestion of using an antibiotic if you think it may save the fish.