my chicks are 16 days old today and i put them in their coop on their 12 day. when it hasn't been raining, we let them in the yard for about 20 min at a time. now, my grandma says i should start offering them grit since they are now in the coop. but i just opened the bag and it looks a little big for them. i bought manna pro poultry grit (insoluble crushed granite). should i start gining it to them or not. and is it supposed to smell like dirt?