ok diet for yellow tang?

Are these large spots, that look like they are under the skin? Or do they protrude a bit? I've seen brown spots on many healthy fish, but they are always smooth and flat. Something that's protruding may be a problem...But I can't think of a parasite that is large--most parasites are very tiny--size of a pin tip or smaller.
 
he is not very big himself, maybe 3.5 inches, their is discoloration on both sides now, brown, white, and bright yellow. he seems to be very very skiddish today, not sure if its because i added turbos and 2 scarlet hermits with a net and that scared him, or what. i may just be over reacting as well. i guess the worst part is, is that i leave tommorrow for a week. so i guess i gotta cross my fingers for when i get hom :sad
 
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