Never had an issue with indigos and mite spray. There are known issues with indigos and other species with ivermectin, but not with PAM or any of the natural sprays.
I guess the question I have is how do you know it was the mite treatment? How do you know you got he mites from someone else? And I second the comment from a previous poster - why the hell didn't the breeder warn you about this sensitivity when you told him the snake had mites?