I have a pair in QT right now that are gobbling up NLS pellets without them falling out... For some reason, I feel like I've seen them with a hole before and chalked it up to some sort of injury. The question then would be whether it's an old injury that has fully healed or one that is more recent and could be susceptible to infection. I'd try to maintain the highest water quality possible, think about treating something for infection just incase and, in the meantime, try some other foods to see if it can keep something down.
Hopefully someone with this experience will chime in with something better for you but this will at least get your thread a bump.
Also, you may get some better responses by moving this to the fish diseases section.
Good Luck
Mike