I have to sets of chicks, right now. The littlest set is in the brooder boxes. I had been keeping the heat off during the day, but now it's 46 and cold here. So it's back on. They're 3 weeks old. The older set is 5 weeks old and they are outside in the "chicky house". What age or what temps before the littles flock can go outside? When should I integrate all of them into the adult flock?