It's fowl pox. There are two forms of fowl pox; dry pox and wet pox. Wet pox is dangerous in that lesions can form inside the mouth inhibiting birds from swallowing their food causing death by starvation. Are there any lesions inside their mouth? It appears the bird in the above photo may or may not have a lesion in her mouth. Let me know please.
You can put iodine or black shoe polish on dry pox lesions, avoid the eyes and nostrils. Either will help dry up infective lesions. Black shoe polish will deter picking as well. As far as the one in the photo, it would be best to put a little neosporin in the eye to prevent any secondary infections, like from a scratch due to irritation or picking from other birds.
It can take dry fowl pox about 3 to 6 weeks to go away on its own. Birds will be immune from that particular strain thereafter.
Unfortunately the outcome of birds with wet pox isnt good unless caught early as lesions can form in the esophagus, crop, windpipe and a couple other areas.