Need an ID

Hi! New here but not new to the hobby. My tanks have always been fish only but this go around have decided to do corals and the sort. Yesterday I was given a leather and a GSP. The GSP has a few mystery (to me) "holes" in it. There is no open polyps where these are. The "holes" close and open but nothing has shown itself from them. I do not know if they are keeping the polyps from opening or if what I am thinking is green algae is.

If they are bad, would a fresh water dip work? Thank You for the help!