I decided I needed more arsenal. So I went to the Feedmill for help. I love the Feedmill, it's like stepping back in time. I swear that the place looks the same as it must have 50 years ago.
After discussing my issues with them, they came up with some solutions. They agreed a dose of Ivermectin would help, as would dusting with the Diatomaceous earth. However - they had an even better idea.
They explained that once chickens become cannablistic, it is often their nature to continue. Some hens begin to like the taste of blood, and won't stop attacking one another. I assured them that my hens were very sweet, and had not become the zombie's they were describing. Regardless, I listened to their solution.
I was astounded. They had such a thing. Tiny plastic glasses that would prevent my hens from seeing straight ahead - causing them to stop pecking at each other. My only objection was that to apply them I would have to slip a small plastic pin through the hens nostrils, to afix the glasses in place. At fifty cents a piece I figured it can't hurt to try. She assured me I don't have to leave them on permanently, simply until the warm weather comes and I can allow them to free range.
The urbanite in me was horrified at the idea, but the farm girl in me knows that the welfare of the hens is what's important, and this will stop them from hurting each other.