I am so stressed. My chicks are 5, 6, 7 and 8 weeks old one of each. I have a chicken tractor, with a ramp/ladder that leads up to the top floor with roost and nesting boxes. I have seen them all on the ladder during the day. Last night, I got in late and looked out back from my deck and didnt see any down below so assumed they went up in their roost area. Tonight it's dark and I just got in and they are all huddled down on the grass in the far corner of the tractor. There is no possible way to reach them. It isn't supposed to go below 63 tonight, so I'm not in horrible fear for their lives, but they have to go up and be inside when it gets colder. Is there something I'm doing wrong? I'm really concerned. They are happy and healthy, eating great! Chirping away and tweeting - like nothing is wrong during the day. Any advice is appreciated.