I have 11 healthy chicks. I received them all at the same time, but two (a new breed to the hatchery) were about 1.5 weeks old. The others were day old chicks. At this point, the two older pullets are about 5 weeks old (maybe 5 weeks and a couple days). I live in Wisconsin so the nights have been getting cooler. Not cold, but in the mid-upper 50's (F). My question is: Can I put only these two in the coop or should I wait a week or so until I can put the whole flock of 11 into the coop? The problem is that I didn't plan on two of them being older than the others and the brooder was slightly small for 11 to begin with (15 sq. ft.).