I think its just the comb your looking at, I got worried about it too when my wyandottes were young. Otherwise it could be fowl pox, but im not sure they could get it at this young of age. Keep an eye on it. If its just the comb it will eventually be bright red.
Looks like it might be fowl pox.... a virus spread by mosquitos. If it is just dry pox... ie not on the mucous membranes inside the mouth etc, then it will just run it's course over a week or two from what I have read. Wet pox with plaques inside the mouth/nasal cavity etc can impair eating and breathing and may need treatment.
I'm not saying this is fowl pox, I don't know. But my flock had fowl pox and recovered very nicely. It took about a month before they were all well again.
I would say that, even if you separate the two, how will you prevent mosquitos from biting the other two.... so you might as well keep them together in my opinion.