Hi. I just moved our 15 CX chicks outdoors yesterday. They are 4 weeks old to the day. They have most of their feathers but are still bare on their 'shoulders' under the tops of their wings. I had a light on in their coop last night. (41 degrees out) When can I quit using the red lamp for heat? Our nights are typically 35-45 degrees this time of year but our days may get up into the mid 70s. Thanks, in advance, for your help, Dave PS. This is our first ever batch of meat chicks.