eliminate moisture and the mites should go away. not good raising mealworms in damp conditions regardless of mites.
mealworms are cheap enough per 1000 from biosuppliers. i no longer bother breeding them for my own pets, as much easier to just purchase some and grow them on a bit if need be.
i hardly use mealworms in general these days though.
id love to see an aro rasied on crickets, locusts, slaters, roaches, worms etc, more so than i would mealworms.
frogs fed on crickets daily: grow like nothing ive seen before.