Offhand, I'd be treating for mites first. Due top the color of her comb, I'd do this quickly. Favus usually looks like a powdery type coating, like they've gotten into flour. Look real close at the feathers, and they appear to have that irregular, chewed on look too. Not only treat the chicken, but remove all feeders, waterers, nest boxes, and bedding. Spray the coop from top to bottom, including roosts. Scrub nest boxes, spray them, and replace with fresh bedding, then return them to the coop. Scrub waterers, and feeders, then put them back in the coop, adding fresh water, and feed. In 10 days, repeat the process, so you kill hatching bugs. Spray, dust, or use Ivermectin pour on being careful not to get it in the eyes, then use colloidal silver on the face, and comb for at least a week, being careful not to get it into the eyes. Rub a medium coating of petroleum jelly on the legs, and feet.