Tang not eating!

I have a new blue tang that was eating earlier in the week n now it won't eat. It has lost a lot of weight. I've tried mysis, red algae, and new life spectrum pellets. It doesn't have a lot of strength to eat the pellets and isn't interested in the algae. Any help would be appreciated.i have tried to isolate it from the rest but it seems to stress it.
 
You might also try regular nori (seaweed sheets used in sushi). All asian markets will sell it and most krogers have it in the ethnic department. Make sure not to get any flavored ones. Also this is a very cheap way to find nori since fish shops sell stuff that's like 8 bucks for 1/10th of what's in the grocery stores that cost me about 2 bucks.
 
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