Hi I have 10 chicken outside that 5 of them are 19 weeks old one is a roo and 5 that are 17-18 weeks old all pullets and i also have 8 5 weks old in the brooder in the house. My question is when do i need to put out the oyster shell for the older ones that are outside in the coop already and with the different ages is it ok to feed them all the grower feed and give the older ones the oyster shell untill they all get to the age where they can all eat the layer feed.