I have all my girls together. Three of them are about a year old and the other four are between 16-20 weeks old and not laying. I have them all on layer feed now. I just don't have the room to separate them. I did take away the oyster-shell, but one the older hens started having thin shells so I put it back out free choice. They also free-range all day, and don't really eat that much feed. So my question is: Is it ok to not feed them grower?