My snakes were doin great, then a couple days after visiting a pet shop, they had mites. That was kind of a pain, but the care is very basic..spray them with the stuff, and change the substrate to paper towels. This showed me the value in using papertowels as substrate, and I've actually kept that as my sub. of choice ever since. Not very aesthetically pleasing, but hey are in racks anyways.
I consider myself very lucky that this is all that I've had wrong.
Well...I had one or two go off feed for a real long time (they weren't sickly though), so I took them to the vet, and they gave them an appetite stimulant. It works great, actually.