^This.^
I bought a crestie in really rough shape from PetCo once just to get her out of there. She has a very obvious case of MBD, and was housed with two males. She was nearly grown and had been there since she was tiny. I also got her two eggs. One of them hatched, so I have her daughter, too. She ate supplemental calcium like it was gecko food for the first few weeks and sat under a UVB bulb (cresties normally do not take supplemental UVB), so she must have really needed it. Now that she's as well as she can be, she'll be re-homed in the near future.
Yes, I know the arguments against buying from a place like that. It was a weak moment, and I couldn't handle seeing her deteriorate.