Help with chicken baldness

[JRB2000]

Silkie has had bald head for many months and now neck is following suit. No signs of regrowth at all. She moulted around Autumn and regrew feathers. Skin seems fine, no different from other Silkies. She is dusted for mites and powder added to dust bath. She is separated at night from feather plucking Pekins, and she is chief Silkie. During the day, I have not witnessed any pecking since we came out of avian lockdown. They have protein and crushed oyster shells in diet. Her wing feathers also tatty. Egg laying ok and all other birds ok. At a loss, any further ideas ?

 

[The chicken Hatcher]

@Eggcessive @Wyorp Rock @azygous