I'm a lurker and a newbie here, and have followed the thread as if it were a good mystery novel. I am a novice chicken owner and according to my friend and mentor, she's never seen most of the problems I've enjoyed over the last 6 months! And I am as besotted with my problem hen, Ginny as Flo's owner seems to be...
My rooster, Bubba, has a bald neck and is missing feathers in other parts too. Ginny's, the one who is mostly intact, fellow hens is suffering from a few missing feathers and I've seen all three of the hens in with Bubba picking feathers from him and each other from time to time. Before it was apparent I had a problem, I was amused to see Bubba finding feathers and calling the girls over for a snack. I have tried most of the things you've all recommended, and am about to go in search of horse manure and beets.
One thing that I haven't seen suggested, and only thought of when I gazed up at my feather collection (from before the picking started I was collecting them to make earrings) is feeding them, well, feathers. If that's what they are craving, why not make a pinata of feathers for them - or would that just encourage them?
Thank you for all the work you have already done which as saved me a ton of time and money - and it's nice to know I'm not alone in this...