Your temps sound fine, I only asked because if (a big "if"?) it's an RI, slightly warmer temps (by about 2*) may help. Don't change a thing.
I truly feel bad for you & especially for your sweet noodle. I've been SO lucky over the many years of keeping so many snakes. Never brought home any mites when
I picked up snakes from an expo, & only once ever on a snake shipped to me. The only other time was one from a pet store & it was obvious, I just went ahead anyway.