Why is my Naso Tang half dead?

[TechGuy40]

So yesterday I noticed her sitting on the bottom, moving slow. No irritation to the gills, no spots, no slime. Looked perfectly healthy except how she was moving. Today I find her half dead under a rock. I moved her to the frag tank, where she can be alone. But its not good. Swimming sideways, barely alive.

Been in the tank for about a month, doing well until now. Grrrr...

[marinelife]

That is very strange, could have been something about the way it was catch in the ocean. You just never know what they use.