I have a flock in Mid Michigan and as the temperatures have dropped, I noticed the tops of my roosters comb getting purple. I don't know how to help them. I have tarp up on the side of my run to block the wind and they have access to their coop all day. I also have a coop heater coming in the mail. I have heard to cut vents in my coop, but I don't understand how that is logical given that it'll release heat. If anyone could tell me how to deal with this, I'd appreciate it.