Oh, and.... Welcome to BYC! @Jchandler
Where in this world are you located?
Climate, and time of year, is almost always a factor.
Please add your general geographical location to your profile.
It's easy to do, and then it's always there!
Hard to know for sure without pics, which can be hard to get good ones.
There are lots of different kinds of mites, most are no problem for poultry.
Are they on the birds or inside the coop?
Google images of lice/mites and their eggs before the inspection so you'll know what you're looking...