Mixed Corn Question

what they speak of as mixed corn is a combination of wheat,maize and barley ! maybe some oat's if your lucky

The highest percentage grain in most poultry feed is corn, so corn is fed every day anyway if one is feeding bagged feeds to their chickens.  When plain ol' corn by itself is being fed for over 50% of their daily ration when fed as training or treats, that's when the imbalance occurs.  As long as it is fed along with a more balanced ration and it doesn't exceed more than 50% of their daily nutrition, there's  nothing wrong in throwing down a handful of corn every day. 

When I picked up my hens from their holiday last October Julie's husband sold me a sack of mixed corn instead of layer pellets . When we noticed the mistake I got it swapped out. My 3 would take years to eat 20kg of corn, a 5kg bag lasts longer than their bag of layers pellets.

Having suffered soft shell I am carefull on how much corn they get, I have layer pellets in the conservatory for them to browse on, as well as that in their run