Problem with Pleco?

I wanted to post this in the catfish forum but this is the only one that allows for pics.

Anyway, here are a couple pics of my dwarf bristlenose. I'm wondering about the pattern on the back. What is that???

and another

Looks like velvet or rust......please medicate asap, he is too pretty to lose!!!

He's had this since I got him in March or April.

Most definitely it is not velvet. The spots are normal!!

I'm talking about that sort of heart-shaped pattern in center of his back. Just to make sure.

Never heard of "rust" before. Is there another name for that???