Hi Mrs. Woods-
Hechicken's advice was right on! With just chick crumbles, you don't need the grit, but once they get to go outside a little bit where they can nibble grass and such, then you've gotta make sure they have a little bit if grit too.
When your chicks are grown and free ranging, they will find their own grit, just as Hechicken has mentioned, but if you have them enclosed in a certain area, and there's no natural pebbles and such, then grit is a must, else they can starve because grit is important for healthy digestion. This is important, especially if you're in an area where it snows alot and they are secluded for the winter with no access outdoors, then you have to supply the grit.
If you can let your chicks outof the brooder for a little playtime each day, and it's warm enough, that is really good for them. but of course you've gotta watch over them to make sure they don't get snagged by a neighbor's cat. I have a little length of fencing that I have in a circle, that I can move around the yard like a playpen for my little chicks. Make sure they aren't in the bright sunlight if you do that so they don't over heat. And I put mine where there is clover and grass--they love that!
Good luck with your chicks!
Sharon