I'm no pro on the matter but I'm guessing they need protein. They should be getting layer crumbles also. I mix scratch grains with layer crumbles and I also have a large tray of oyster shell for them to eat as they wish. And several times a week I give treats such as canned fish, oats (the kind you would make oatmeal out of), bread, vegetable scraps as long as there is no butter or grease used to cook them. We also go to our local convience store and buy the remaining food left at the end of the day and feed the hamburgers and some of the other stuff that isn't deep fried. Yes, chickens can eat cooked chicken. Meat is protein. I also will cook extra scrambled eggs so there is enough to share with my chickens. I wash the shells, let dry then crush in my Ultimate chopper and add that to their food also. It makes more of a powder out of the shells. Provides calcium. They get apples and grapes, cantelope, pumpkin. Pretty much any fruits and vegetables but no citrus.
So to sum it up, I feed them pretty much anything except for greasy foods and citrus. I don't drain the water off the canned fish when I mix oats with it. I drain it when I don't. And I always add grit to all people foods I mix up for them or toss a handful in their food dish.
They also are let out very often to free range.
When you have a meal with left overs, just put them in a bucket everyday for the chickens and give them to them. They may not eat it at first or all of it but eventually they'll get used to it and be waiting to see you with a bucket. Mine get all excited when they see me carrying a bucket or a bag. That means they have treats that day. Oh bread, did I mention that. I give mine the ends to the bread in the loaves or what we toss out as long as it isn't moldy, biscuits, cornbread, rolls, buns. I have one that will jump up to eat right out of my hand. She is more of a goat than a chicken but it's pretty cool to see her do it.