If you zoom in on the bill there are more than one lesions, they are also generally occurring on the sides, rather than the top of the bill. This can occur when the bird is sticking its bill through an object, such as wire repeatedly creating sores and scabs.
I really do not think this is a serious issue, nor do I think they are going to continue to spread at an alarming rate.
The puckered/shrunk look around the lesions, in my experience, is common with any sort of bill injuries due to the nature of the bill material.
If you want to get to the bottom of this, try sitting out in the run, and watching for any sort of action (such as the one above) that could be creating damage to the out bill layer.
With something like this, a diagnosis will be found more accurately via observation of the flock.
