Excellent post @ChickenCanoe . I am in the "Chicks need grit" camp. I believe they should have it shortly after they figure out what the chick crumble is all about! God gave them a gizzard for a reason, and it should be used.
My chicks also get: A plug of sod. Poultry Nutri Drench. And scrambled egg. And their feed is fermented. IMO, these are the only treats a brooder raised chick should get until she moves out of the brooder.
This season, I have 22 chicks being raised by 2 broody hens. B/C they have been outdoors in the run, I have been somewhat lax about giving them the above items. Mamas are seeing to their needs, including giving them greens, grit, insects, worm and deep litter (Yes, they chow down on some of that deep, rich, fragrant, black compost in the run.)