Are the two hens with bare necks higher ranking or low?
I had three of my hens with similar bare necks this summer and wondered about the cause as I never saw anyone feather pecking. I even went to watch at night to see, if it could happen only at roosting time. It did not.
Then I caught them way back in their large enclosure behind some bushes sticking their heads through the wire fence to reach a certain area right behind it. By sticking their heads through the fence several times every day they damaged the neckfeathers similar to what your two hens look like.
To help prevent boredom you could give them whole carrots to work on.
I had three of my hens with similar bare necks this summer and wondered about the cause as I never saw anyone feather pecking. I even went to watch at night to see, if it could happen only at roosting time. It did not.
Then I caught them way back in their large enclosure behind some bushes sticking their heads through the wire fence to reach a certain area right behind it. By sticking their heads through the fence several times every day they damaged the neckfeathers similar to what your two hens look like.
To help prevent boredom you could give them whole carrots to work on.