I am in Florida which has hard water. Tons of iron and lime in the water. When this happened last time, I was feeding 2 rat pinkies at a time. The vet said it was caused by feeding more than one food item so I switched her to 1 rat fuzzy per feeding. Now it has happened again. I have 4 other 2011 hatchlings and they don't haven't had any problems. The humidity in her tub stays around 60%. The temps are 87 F hot side and 80 F on the cool side. I feed them once per week. She sheds with no problems and no sign of mites.