I have some chicks on order from our local farm/feed store. They will not arrive unti the first week of April. The store will have some chicks in earlier on a first come first serve basis in Mid-March. If I get chicks at different times, I know I have to separate them since they will have different temperature needs. Will there be a problem introducing the younger pullets (at 6 weeks old) to the ones that will be three weeks older and already in the coop? Should I be patient and just wait and get them all at one time instead? This is our second time around raising chickens. We did it four years ago and enjoyed it so we decided to start again. The older chicks would be Buff Orpingtons and Auraucans and the younger ones would be White Rocks and Black Austraslorps.