It may be pox, I can't zoom in to see closely. If it's pox, they will slowly darken and dry up to scabs and eventually fall off. Most birds do fine with no real issues with the dry form (which this appears to be). For birds that get the less common wet form, it has lesions in the mouth and throat and that can be more serious and require more care. I don't isolate for this unless the bird is acting sick. I just keep an eye on them, make sure they are eating, drinking, and acting normally. It is transmitted by biting insects, usually mosquito's, so likely they are all exposed if that's what it is. I've had just one single bird show up with it, or several. Reducing your mosquito population can help. Screening coop windows or having air blow over roosts at night can help keep them out or keep them from landing on stationary birds during the night, that is when it happens the most. If it's pox, then likely she will get through it just fine with no real issues. Once they recover they are more resistant in the future and shouldn't get it again.