Okay, this might be a really retarded question because I just don't know much about the teeny little guys, but is it possibe that, wuv, in the case where you said one of your teeny little guys ate a huge worm that it got into his belly, therefore expanding his belly so much it pressed up against his swim bladder for a while giving him problems? Then as it got digested it went away?
I remember reading somewhere that some fish are born with deformities, and some fish just have weird shapes, and because of one of those 2 things, something in their bodies ends up pressing against their swim bladder so they're just destined to have problems their whole life...