I don't have any advice to contribute, but I have a similar situation going on with my hen. She has feather loss in the same area that I can confirm is not caused by other chickens because she is by herself and has been since April.
Were your hens' faces more feathered before this issue came up? My hen has feather loss on her face that looks similar to your girls. She also has some loss at the base of her comb.
Were you able to find a solution for your flock?
I hope so!!! If you were, would you mind sharing it with me? If you weren't, can you share how it's progressed?
I have searched high and low, but it seems that there's a lot of contradicting information out there, which doesn't in still confidence in how to proceed.
Thank you for your help,
Kati
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