Hi all! I have 5 pullets, all almost 19 weeks old. Two(SLW and EE) are acting like they might start laying soon, very red combs and they are getting more vocal by the day. The other 3 don't seem to be getting ready to lay. I know it can be awhile yet for any of them to lay but my question is, when should I start offering oyster shell free choice? Right now I feed them Purina starter/grower. I want to finish the bag before I switch them to a layer feed. Is it bad to feed oyster shell free choice before they start laying? Thanks!