Chick crumbs don't need grit. They are a fully formulated balanced diet of *stuff* that breaks down very quickly when swallowed.
Some may contain grit, the one I buy doesn't.
Chicks allowed out, eating grass and bugs will need grit. You can get *chick grit* which is smaller than the standard stuff, but if the vast bulk of their diet is starter ration, they will probably find enough small grit in the run.