OK.. so my vet said he sees lot's of feather damage. But no irritated skin associated with the microscopic type mites, so he wouldn't even know where to scrape to look for mites. In other words he doesn't think I have an issue. He said lice CAN be a problem. Which I have seen on other birds and treated my whole flock (with permethrin), and he didn't see any evidence of lice being an issues. He said that with my animal load (currently 28 hens, 2 roosters, 42 grow outs and 9 ducklings on 1 acre. Called it intensive farming).. there is no such thing as a season regardless if you have mild or harsh weather conditions that might usually see diminished parasite activity. So learning what you have and how to keep it at bay and developing a routine that includes altering medications to avoid resistance if you need to use them.
Ahh!

I took my worst looking, best behaved hen and I'm just afraid he missed something.

He is an avian vet with lots of experience and I trust his opinion!

I guess I'm a little paranoid, never mind the over thinking OCD.

Oh, and I was prepared and already spent $40 on Ivomec. Which upon reading the label said when used in cattle that the meat was not safe for consumption for 48 days! I would assume meat from chickens would be at least that long. So I probably wouldn't try to treat any birds I was gonna eat any time soon.

But if it was a life saver for my whole flock would definitely pursue off label use with caution. When I get fecal floats done for worm count, I probably won't use that unless that's the only kind that will solve the issue. Otherwise I would TRY to go with something that is on label and with less withdrawal time for eggs/meat.
I will continue to do checks and not worry about my current damage until molt, unless it appears to be getting worse. Always vigilant. Kind of relieved though as stated, somewhat skeptic.
He did see the striations on some feathers and said it was an indicator that something happened when that feather was still growing in during (called) the blood growth phase I think.
A trip to the vet is not feasible for many, wish I could be more help. Hope you get yours figured out.