Ok, Remove all corn, scratch and anything except their pellets, they've gotten spoiled and just pick out the tasty stuff instead of eating the healthy stuff. Like children wanting the cookies and icecream over broccoli and chicken. They are suffering from serious nutritional deficiency, especially in protein. That's why they're eating each other. They might not eat it at first, since they're used to two options but any healthy chicken will eventually eat if there's food. Don't give them anything other than their feed for a few weeks, and then limit any treats to only once or twice a week.
Actually, you might want to try a higher protein feed like chick starter or flock raiser for a while. Good luck. Remove the decon, the chance are too high for the chickens eating it.
