My chicks are 5 almost 6 weeks old and are in their coop. I haven't used a heat lamp at all this week and they seem fine. I live in Belleville, Michigan but the weather at night hasn't been too cold so far. I thought chickens needed darkness at night. Do they? Or should I keep their 100 light bulb on??? I've been turning off the light about 7:30 p.m. and I hope they go right to sleep.