Check our caresheet to compare to your temps and humidity. Get a vet appointment and I'd suggest you warn your parents to watch their snake closely. Since these snakes were housed together and kept incorrectly, the other one may also be brewing up a nasty RI.

Only an experienced herp vet can diagnose and treat an RI. RI's do not go away on their own, symptoms may disappear temporarily but they don't just heal up. You do need to see a vet and you very likely should be contacting that stupid pet store who sold you equipment with a snake in it and stuck you with the vet bills on snakes they didn't properly care for. Did you get any type of health guarantee from them?