Doing a routine check on my buff orpington, I noticed areas of gray dust near the base of her feathers, just below the vent area. Did she take a really good dust bath and just hasn't shaken off all the debris? Or is this the start of mites? It doesn't look like the mite pics I find online, but those may be extreme cases. I'm fairly new to chickens and have not yet had to deal with mites/lice, so any advice would be appreciated. Thanks.