One thing to watch for though is sneezing, runny noses, or any other signs of upper respiratory infection. You can give them org apple cider vinegar and/or probiotics in their water to help them get through the winter.
Yeah, just leave it. It will resolve on its own. It doesn't look like the worst condition. Can you move them to a place where that is warmer, or no draft? Or place a blanket over their coop?