Sorry for double posting, but it's about these puffers again. My first two died two weeks after I got them, which didn't really surprise me since I knew I bought them sick.

Anyway, I have another puffer who is healthy as far as I can tell. But when I got him at the store, his belly was completely white. Not a smudge of black on him. As soon as he was put in the take-home bag, he turned black and now he won't turn white again. What's wrong with him? D: