She is a great momma and has been taking care of two little chicks. She is not laying (because she went broody last month and we gave her chicks to raise) and appears to be eating and drinking. She is active and constantly foraging. A three weeks ago we did have a chicken die. I thoroughly cleaned the coop with bleach and locked them out until it dried. 5 days ago I notice feathers missing from her bum. Skin was not red, looks normal and new feathers were growing in. I did not see any mites but I cleaned the coop again over the weekend, sprayed with a mixture of garlic water and acv and put DE down before pine shavings. The first picture is a week ago and the second picture is today. She is 5 years old. Should I be worried?