yeah, I agree, it sounds like you have a mite problem (well your snakes not you!). It could have killed your other snake if there are lots of them, they feed on your snakes blood you see. Kinda like fleas on cats and dogs. You will have to completely disinfect your snake tank and ALL cage decor and find some mite killer to use on your snake (not sure what you have where you are so you'll have to ask around (vet, breeder etc). If you have other snakes check them too. Mites are ba*t*rds to get rid of! Oh, and if you have plants in your tank (real ones) get rid of them. I had mite problem a while ago (they were windowsill mites so they didn't do anything to the snakes thank god) and the mites were breeding/ living in the plant soil. Had to ditch the plants and replace them with plastic ones. HTH