Mystery Affliction

I have a Zebra Danio which seems ill. It has been housed in a 10 gallon tank
with 4 other Danios, a female Betta, a Ghost Shrimp and a snail. All water
parameters are fine (0ppm ammonia, 20ppm nitrates) and all other fish are fine.
When feeding last night I noticed it off to the side, not eating, kind of
shimmying in place. It looked swollen but no pinecones and it was moving it's
mouth a lot and breathing very hard. I netted it (quite easy for a Danio, so I
know something's up) and moved it to a 1 gallon tank. Today it's very still,
mostly staying at the bottom of the tank very still, not eating. When it does
move it either shimmys in place again or darts around (but not flashing). It
also looks crooked just behind the eyes...almost halfway down the body. I did
catch it with the net there and am not sure if I damaged him or it was there, I
had never noticed it before (tuberculosis?). I vacumned and changed the water
yesterday and wondered if maybe I got it with the vacumn. As I said, all
others are fine with nothing out of the ordinary happening. I did a search but
aside from the crooked spine I could not find anything that sounded accurate.
Any ideas/help would be greatly appreciated.