Each year some chickens go through a hard or soft molt it seems. I think you want to make sure you increase the protein in her diet to help her go through it. Keep at eye on pecking though. I have 5 chickens out of 16 going through a hard molt right now.
We used Elector PSP. We were very careful to only apply a very small diluted amount. I think it was 3 mil per gallon. We did spray near the vent though 😬
We treated our rooster for mites a few months ago when we noticed he started limping. We kept an eye on him to make sure all the mites were gone. He kept taking turns on each leg, skin and comb looked healthy and he still seemed strong so we hoped he would improve. Unfortunately he didn't...