I just brought home three two-tailed bettas, Comet, King and Alnitak. Comet and King seem to be perfectly fine, but when I put Alnitak into his bowl I realized that his left gill seemed to be dislocated, as if it had popped off its hinges. He also seems to be less active than the others, and has a tendancy to let himself fall over and lay on the bottom of the tank. The most worrisome of his actions is when he swims around; he keeps tipping up onto his tail, with his head pointed at the surface, as if he can't keep himself horozontal. I have also realized that his pelvic / ventral fins (first two fins on underside of fish) are shrivelled and twisted, and these areas are black.
If he was behaving propperly I wouldn't be nearly so concerned, but as it is I don't know if Alnitak is just stressed from the move (which happened yesterday) or if it's something worse. Considering the physical signs, I really think that it might be a problem, and I would appreciate any help from the community.
I've uploaded a few images of Alnitak. The first is the best picture I could get of his ventral fins, and it also shows the extent to which his left gill is open. The second shows him lying at the bottom of the tank, which he will do for a few minutes straight before moving again. The third is him resting on his tail at the bottom of the tank.