I am getting some new chicks tomorrow (should get that PO call in the morning). This is a second shipment because not enough Cuckoo Marans hatched to fill my order. I now have some that were received last week that are 9 days old tomorrow and don't know how or when to introduce them to my newbies that will arrive tomorrow. Should I keep them separated for several days, weeks, or what?? I've never had this happen before. BTW, I have about 18 and am getting 10 more.