I don't say "definitely" with pics too often, but this is defiantly not ich, it has way too big. I agree wit Sandi54, I'm almost sure its lymphocystis. Google "marine ich' images; you'll get pics of very infected fish, but just look at one spot. Lympho is a virus, some think it flares up with stress. This will almost always disappear with good water, a good diet, and time.