Naso Tang Sick?

[TaioneReefer]

Hey Canreef,

Past few days I noticed my Naso has started to get skinnier and skinnier, and today he just dont seem to be swimming too happily(almost as if hes wobbling side to side unbalanced)

as well as his stomach is alot skinnier like the yellow tang when i first got him.

all the other fishes are fine, just the Naso, he ate a bit today, but didnt eat as aggressive as he used to

I also did a water change today.
and the nitrite, nitrate and ammonia is all 0
Thanks.