I follow my great grandma's advice... feed a growing baby as much as it will eat! Within reason of course, I measure puppy food and offer snacks through out the day. But with baby chicks, I keep the feeder topped off 24/7 and the same for my grown flock, topped off at all times in spill proof containers to keep waste down. Chicks are growing fast, and need high protein for all those feathers coming in. You never want to limit chick feed, or choose a cheap feed without all the minerals and protein levels they need.
Clean water 24/7 is a must as well, never let it get empty or filled with shavings/bedding from them scratching around.