In your area, I would my first thought would be fowl pox, my second is favus. What color are the spots? Here is some info on favus:
A Pocket Guide to
By Paul McMullin
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A fungal infection, Trichophyton gallinae, of chickens and turkeys. It is very rare in commercial poultry production.
White, powdery spots and wrinkled crusts and scab on comb and wattles.
Thick crusty skin.
Loss of condition.
See signs (above).
Formalin in petroleum jelly.
Good hygiene of facilities, culling affected birds.