Get someone who is knowledgeable to show you how to body condition score a chicken. Turn them over and examine keel. Birds should feel really dense when you pick them up and not lite, frail, boney.
What you are aiming for is adequate nutrition balanced to needs of birds based on stage of life/production. Corn is lower in protein than good layer pellets. For example if corn is nine percent protein and layer pellet is eighteen percent feeding a pound of each lowers your ration to only thirteen and a half percent.
There is good info out there about animal nutrition. As someone suggested get best you can afford to feed. Stick with a brand or mill that you can rely upon to always have quality product. Once peeps are three or four weeks old I go to feeding them all they will eat in say thirty minutes at least three times a day. In between they can clean up what they spill. Same for my adult birds, I don't leave feed out, but feed at least twice a day. Leaving feed out at night just feeds rats and mice. If temperature is below freezing they get fed more, especially fed well when going to roost and when coming off roost. And water, clean enough for me to drink twenty four seven three sixty four. Water is probably most neglected nutrient in a nutritional program.