I assume it’s canker?
I believe many here have treated that with over the counter fish zole. I know our tractor supply carries it in the chicken section.
I just recently had a mite problem and dust bathing is a struggle with frozen soil. I tried organic methods, but it wasn't working so I broke down and went with permethrin powder.
I got this off of Amazon..
https://www.amazon.com/gp/product/B01KAI8NH8/?tag=backy-20
And filled it up with...