crust on face

Hello, I have some free ranging chickens and they all seem to have caught this disease that encrusts their face with bumps. I did some research and thought it could be mites or fungi, possible favus, but I am not sure. Can anyone help identify what it is and advise me as to how I should handle...

Our silkie hen has been sitting on eggs for awhile and we finally had one successful hatch yesterday. She has been isolated from the flock for about a month, once she started to go broody but about a two weeks ago I noticed her face getting crusty. She has also lost feathers (though she was a...