looks like fowl pox. You can apply antiseptic to the scabs, and you'll need to remove any scabs that have a chance of obstructing the chicken's ability to see or eat. There isn't a treatment, (or so I hear) and if you want to prevent this in the future, you need to vaccinate your hens. here's a helpful site: https://edis.ifas.ufl.edu/pdffiles/VM/VM02100.pdf you should sepperate the affected hens.