Essential Cookware Sets white stain

Probably. A chalky white residue can be calcium or magnesium from hard water. It's easy enough to remove with a bit of white vinegar or some Bar Keeper's Friend. In the future it might be worth it to just do a vinegar or Bar Keeper's swipe when you wash, to avoid it. I have hard water where I live, and an in line water softener- but I still get the odd calcium residue and this is the way I keep it at bay.