Tang wont eat, bacterial infection?

Question
Have a 55 gal. set-up with live rock, some simple corals, snails, crabs, and a clown fish.  Bought a large yellow tang from store several days ago, looked like a healthy guy.  First two days home, he ate algae and some plants, but didn't eat flakes or pellets.  Haven't really seen him eat in past 4-5 days since, not even algae.  He has developed cotton mouth and is getting white specs on his body, and his eyes are a bit cloudy.  Just began "triple sulfa" treatment yesterday; cottonmouth is better, fewer spots, but today he looks really skinny, and still has not eaten.  What do I do?  I do have another tank that only has crabs and snails, 29 gal, so should I move him there?  Then what?  Thanks for your consideration and advice.  It makes me sick to think I brought him home to die.  (BTW, clown fish eats and appears good, hasn't changed since we got him a couple months ago.)

Answer
Get him out of the tank, it sounds like bacteria or parasite. You could have very much brought him home like that just the stress of moving him from tank to tank brought it out faster. May I suggest establish a good relationship with a LFS. See is he will let you put deposit on a fish, leave it at the store for a week or two. I have this set up with 2 LFS around here, you also have to be good to them. If I find something online i will always give them the opportunity to get it for me.