[naesco]

The kole tang tends to get a bit cut up as it darts around when it is new to the tank.
I would not risk the possibility of either ich, a fungus or minor bacterial infection setting in.
Please look at doing the garlic extract feeding until it clears as a preventative measure.
Although kole like a variety of food they need film algae as part of their diet.That is what you see them constantly sucking on rocks and the glass.
Leave part of the back glass "unclean". Also it is a good idea to put some smooth stones in a pile in some corner. As well as the ideal film algae feeding station, it a great place for pods to hide and multiply.