Looks like you got two great answers. Most Dumerils have that white spot under their jaw, not all. I have one that doesn't, but it's a very common trait. Mites irritate the heck out of snakes. It's not uncommon to have a bad shed when dealing with mites. I can't say that I'm a pro when dealing with mites though. I only had one instance of them and that was probably 10 years ago. I now treat every quarantine with PAM to ensure they stay out of my collection.

Good luck and keep us posted!