I had to return a dead corn snake to Petco. They were feeding it crickets.
And when I told the manager (who takes care of the reptiles) that corn snakes do not eat crickets because it's bad for their digestive system and has no nutritional value, he completely ignored me and said "you got your money back didn't you?"

Petland on the other hand is where I got my very healthy corn. Other than cohabbing they seemed pretty knowledgeable about the reptiles. The thing with pet stores though, even if they can sell you a healthy animal they won't know crap about it. They have no clue how old it is, what gender it is, what morph, etc.

From now on I will stick to breeders. There's also a reptile expo every 2 weeks where I live which is very convenient if I ever wanted another animal.