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X2 she is molting. They often begin at the neck and work downwards. Depending on the breed, it can take anywhere from one week to three months to finish the molt process.
Protein is important during the molt. Foods such as quinoa, meat scrapes, fish, mealworms, etc should all be fed while the chickens are molting. Feathers take up 85% of their protein so losing all their feathers means they will lack protein. If you see your flock eating feathers then they need more protein.
Also, watch for bulling and feather picking during the molt. Sometimes chickens peck at the bald patches on the molting birds so it's important you watch out for this. If you come across an injured bird, isolate her, clean her wound, give her herbs and let her heal.
Good luck!
