2/3 of my turkeys have a black circle on their beak, their heads are turning purple and there's crust around their nostrils/beak, what is going on?

[White feathers]

I currently have six turkeys (Broad Breasted Whites and I've had them for about three months now. This is my first year raising Turkeys, usually there running around doing whatever it is they do. A week and a half ago one of them developed a black circle on the right side of their beak. At first I thought it was dirt and didn't think much of it. Then it got bigger and more of them got it. As of right now 4 of the six of them have it. In addition to this their heads are turning purple and they have crust around their beak and nostrils. They are still eating but they have been less active. What's going on with them and what can I do to help them?

 

[R2elk]

@casportpony

 

[sarahere4u]

Maybe Fowlpox? It's been a few weeks since you posted this.. Did you figure it out already and how is everyone doing now?