I have to say, I have only ever heard terrible things about petland, especially the notorious puppy mills. Personally, I only buy from breeders because I know exactly where my snake came from and exactly what it was eating. That being said, pet stores are also money hungry, for example, petco/smart selling normal ball pythons for $80 where they're only worth around $20 from a breeder, $8 imported.

BUT it only matters that you are satisfied with your animal. Mites are visible on the skin, you'll see them crawling around. If it eats, even better. Hopefully your snake is healthy