That's more of an opinion question. Some feed anything and everything from day 1 cause with a hen free ranging they'd get all sorts of food. Others feed nothing until they are old enough to go with the flock. Others are somewhere in between with either a certain age they start treats or certain treats they feed to chicks. Everyone will have a different answer. Just make sure they are eating their chick starter. When you give something new they will sometimes fill up on only that which is especially bad if it's inedible like grit or sand.
If it's something that needs ground up, think about whether you'd have to chew it, they will need grit of some type. Chick grit can work for standard chicks but I don't know about if you have bantams. I can't get it here. The smallest grit I can get is barely small enough for my adult bantams. I just scoop sand out of my horse arena. I don't hatch large batches at a time so 1 cup often lasts until they move outside where they can find their own grit and/or use the grit in the coop.