They all grow at their own rate, but from the pictures he looks ok.

The 15% rule, and feeding a rodent that is as wide as the snakes widest point are both good ways to determine rodent size for young BP's

I feed my really young BP's every 4 days. Once they get into the 500-600 gram range I move them to an 8 day feeding schedule.

I'm no expert on IDing Ghosts but he doesn't look like one to me. The way to tell for sure is when he sheds. If the shed is clear then he is a ghost... if not then he is not a ghost.