The photos aren't quite close enough to tell for sure. From what I see, it does look like it could be fungus because the white areas stand far out from the fish. Some bacteria may mimic fungus so you can't rule out bacteria either. If you could zoom in on one of the effected areas, I might be able to say more. It might also be sloughing of the fish itself. If a fish becomes irritated enough (usually from poor water quality or poisoning), it will slough off its slime coat and sometimes even scales fall off. I'm sorry I can't make out more to be more sure.