Parasites wouldn't make him look 'ashy'. Is it possible to post a picture of the snake? External parasites like mites are tiny red or black dots that you'd see moving around the eyes, under the chin, and around the vent especially.

It may have a stuck shed. Is his skin kind of wrinkly and stiff? You might want to soak your snake in warmish water for an hour or so (not so deep that he has to swim) this will loosen shed skin if that's what he has. Normally they shed within a week of their eyes going blue.