This is very possible. It happens in my beers with a yeast that hasn't dropped and compacted well, or hasn't had enough time to. It can produce some small brown spots on top of the head.
It's normal, have this all the time if I'm picturing what you're talking about correctly. Just the head particles sort of glom together and it looks like as you said, mold on cheese. It's just the way the proteins flow, nothing to be concerned about.