I think that if you switched to the chicken layer feed and let them free range it will be the best of both worlds for the chickens. They definitely need more than just corn, even if you ferment it. The corn will make great scratch and also can be added into the chicken layer feed ferment. I don't think it was the differing of the feed that messed them up, but the food meant for dogs. I have changed feed brands 3 times on my young flock and they haven't had any problems. Dog food isn't bad for now and then, but as a mainstay it doesn't have what chickens need. Dog food has a lot more protein than chickens need and their bodies can't handle the excess well. It doesn't have the calcium needed for egg production either. Just my 2 cents.