Thank you for posting a pic, that is helpful. Here is a recent pic of my 3 Choc. Orpingtons at around 20 weeks. You can see that the middle one still hasn't feathered up quite right. Also, he can't fly because his feathers came in crooked.
We insulate the coop and use heat lamp set on timer... we also have to have lights on a timer as our days are getting darker already lol but ours have always laid through winter hoping to hatch some more choc eggs next summer in hopes of a roo and few more hens you have beautiful chocolates