My youngest batch of chicks is a few days shy of 6 weeks old. They have been in their coop for weeks with free access to their run. For a week now they have had free access to the yard with the ability to go back into their coop or run at will all day long. At night, they are closed in their coop run with the heat lamp in one corner. We are in upstate NY.. nights are around 50-60 this week.. who knows what next week will bring.. some nights we are 37.. the next night we could be 45.. weather is nuts lately.. My ??.. is it time for the heat lamp with infra red bulb to be turned off? There are 15 chicks total.. 9 of them are nearly 6 weeks old, the rest are 8 weeks old.. Aside from some head fuzz.. they are feathered..