grouper not eating

I have a blue spotted grouper who hasn't ate in two weeks maybe more. He shares a 125gal tank with a 7 to 8 inch map puffer, the grouper is about 5 inches. I had the grouper first, for about 3mth and the puffer 2mth. Three weeks ago I spotted what looks like nicks all over the groupers body. I don't know if it is ick or what. About the same time the grouper stop eating.
I don't know if the puffers attacking the grouper or what. How will I know if it is ick or not. And I would like to know if that's the reason why he stop eating.
Please send me some solutions and answers, I don't want to lose him.
 
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