When mine had avian or fowl pox, the had a lot more lesions than that. Fowl pos lasts 3 weeks then suddenl disappears (the dry form.) I suspect what those are, are peckng injuries, or a similar minor injury.
My BO's have similar marks to that, and it's from running through the scrub chasing each other around.
I think yours are injuries, rather than disease in this instance. It could be from pecking, or from accidental scratches when they go under bushes etc.