We have some black australorp chicks that are currently in their 4th week (so they're 3 weeks old). They are sleeping without any heat source at night and seem to handle our 75 degree bedroom just fine. In the day we keep them outside in their run the entire day where it is around 80 degrees in the shade. The coldest it gets at night outside is 67 degrees (we measured the temp at the coldest part of night). I'm hoping to move them outside once they are 4 weeks old, but I'm wondering if dropping from 75 degrees to 67 is too large of a jump. Should I wait until they are maybe 4.5 weeks old?