Chicks on starter do not need grit BUT I give all my incubator babies a large dish of yard dirt/sand starting on day 3.
Here is why: when I have a broody hen with chicks, she starts picking at dirt/sand on day 3 of the babies life and encouraging them to partake of the sand/dirt. This also allows the young chicks to eat any treat you want to feed them - mine as young as 5 days of age will get mealworms, household foods - breads, veggies, meat - ect. They also love to dust bathe in the sand/dirt to help with all the itchy new feathers starting to come in.
I do not feed chick starter or medicated feed - I feed a multi flock food called Flock Raiser.