Two of our chickens have these dots, one is a little more obvious then the other and the australorp has chalk like appearance around the dots.
Fowl pox I am pretty sure. It they act fine it will just run its course and go away. If they start to get uninterested in food or water you will need to get them to eat as that starts a downward spiral. Dry pox like that is not very bad on them and they do fine.
I never have unless they get a secondary infection in them. There are different manifestations of pox. This is the best one to have. Less problems. Some people put iodine on them but I never have.