My ducklings are 6 weeks old. I just ran out of chick grit but I have regular grit. I'm wondering if they're too young for the big grit and should I buy another bag of chick grit (which I know will barely get used)? They've started going outside for about an hour or so each day depending on weather, and I see them eating a lot of grass and dirt, but I don't know if there's enough grit in the dirt they're eating? Thanks for any advice.