I'm not sure if this helps...Two out of my 5 birds had similar feather loss like yours. One of my EE's neck looks just like yours. Since I didn't see one feather on the coop and I saw one hen pick and eat a feather off another one, I knew it was feather picking. I will be putting peepers on all 5 to discourage this behavior. I choose to put on all 5 instead of just the "picker" just incase someone else has picked up this behavior without me being aware of it.
Mary
Mary