My three babies are a little over 10 weeks old and I haven't been giving them any solid snacks up to this point because I couldn't find chick grit. I just checked the back of my box of chicken grit, and it says that it can be given to chickens 10 weeks or older. The only thing that I am worried about is that the maximum calcium that could be in it would be 13.2%, and I don't want to give them too much calcium. The grit is all ground granite. Should this be ok for them or should I just order some chick grit offline? Thanks!