My Blue Orpington has started picking/pecking herself all over...under her wings, her butt, her chest. She whips her head around like something is attacking her. I had my husband hold her while I examined the base of her feathers yesterday, and I saw nothing unusual. But I dusted her all over with Sevin dust in a nylon stocking. Today, she is still battling something. I picked her up and checked again and today I see large light brown flakes at the base of her feathers near her vent. I feel terrible. What can I do to help her and give her relief? I have Sevin dust and Ivermectin Pour-On (5mg ivermectin per mL) Edited to add photos. Also, I am told it doesn't look like there are any mites/lice. Thoughts on how this might occur?