Some help please - pic added

[Montana]

i agree it sounds like black ich, I just went through this with my yellow tang, all i did was fresh water dips once a day for no more then 3 min for 3 days and the ich went away, if you notice the fish being stressed out. like trying to jump out of the plastic container stop, also some people recomend formalin dips but i dont know anything about using that method.