I got a good look at one of my girl's vent today and I believe I see lice (light brown, very small crawlers around her vent and bottom.). I'm going to use sevin in hose to treat but I've been thinking about how it started. They have access to a yard where they take lots of dust baths and spend most of their time. They roost at night in 2x4 planks. I'm using the DLM with shavings and DE in their coop. Is that my issue? Do I need to dig out the shavings more frequently than I am now (every 3 months is my current). How much DE do u recommend to use to prevent the issue? this is my first time with this in my 17 months w a flock...what else do I need to think about?