I made that mistake with her, but she lived for a long time. I had a lepidogaster, and she was eating well and all and I got sick and she stopped eating and my family couldn't do anything about it and she passed away. She was most likely wild caught and infested from head to toe with parasites.
Another recommendation for buying animals, especially reptiles, is get it from a breeder. Never buy from a store. Even a local pet store, I learned this the hard way. Pet stores DO NOT take proper care of their animals. Especially stores like Petco and Petsmart. Don't ever get from them unless you want a long list of vet bills. Its a no-no. bad bad bad. nononononono.
Kingsnake.com has an enormous list of breeders and suppliers. Go to reptile shows and buy from there. Just not from a store, its a nononono. They are likely to be wildcaught, sold too young, or just in poor health to begin with.
I should have caught this with my youngest, not doing well, leo, pastel phase. Now I know thanks to Golden Gate Geckos. Her two month old she sold me was ten times bigger than my baby was at two months. So I know now what size a leo should be at about 2 months. And as an adult as well, since I have my cute little high yellow female. She's getting fat, trying to figure out how to get her off mealies and back to some crickets :S.
As for MHD's, there is a lady that talks a lot in the MHD forum that breeds them. I think she only has one subspecies right now, but she takes good care of her babies. She had an article in Reptiles recently on MHD's. She can give you a lot of advice on MHD's, the do's and don'ts etc.
Anyway. I know now that whenever I think something is wrong with my animals, they go to the vet. Period. A simple little 11 dollar checkup is better than having $200 of bills from medicine and stuff they have to do in the office.