after a couple of weeks in the coop, my chicks suddenly wouldn't return last night. It has been chilly at night so i had a heat lamp on to help coax them inside. Now however, the overnight lows are only in the 40's so last night i left it off. Now i've been up all night checking on them because they won't go back in. I put the light back on thinking they were used to it, but that didn't help. So now it's 4in the morning and i just checked, all still nesting together under the ramp to the coop. it's currently 52 degrees, so they're not cold but i thought it was norm for them to go back inside. Do chickens often choose to remain outside, or are they afraid to go back in for some reason?