Not likely to see plumage mites as they burrow under the skin next to the feather shaft.Thank you, it does sound like that is possible.
I am planning on getting her to the vet today even if it has to be an emergency visit (no appointments were available yesterday and they suggested observation and calling today...).
No signs of mites. Overbreeding is the likely reason for the feather loss, they have been together since they were old enough to be separated out and he has been good until now.