I have used sevin successfully along with bedding changes and no-pest strips.
It's a long, drawn out process that's dangerous for snakes but it works if you got a week. I think this method has fallen by the wayside in favor of less dangerous methods.
There are better methods now that include nix shampoo, (BK and BKII), and provent-a-mite.
I have no experience with these methods, and I hope I won't have to learn.
I'm sure someone will be right along to fill up your skull to the top with knowledge.
Even with these preferred methods, it's still a minimum of 2 treatments, a week apart. (To kill the eggs, once they've hatched.)
If you have furry pets that have free reign maybe it would be a good idea to restrict them from the area, or treat them, as they may wind up as temporary hosts, reinfecting your snakes over a week later.
If you lost a corn to mites it sounds pretty bad.