I have 6 Chickens and they are 8 weeks old. 3 EEs and 3 RIR. They have been outside for the last 2 weeks with temps dipping to mid to low 40s. I have not seen any issues. However, tonight the low are supposed to be in the mid 20s. Temps are supposed to normalize tomorrow. The coop has good ventilation but not drafty. It is not supposed to be windy tonight, just cold. Any reason to be concerned or a reason to heat the coop tonight? I know they are cold hearty. They are pretty well feathered except for underneath their wings (when I lift their wings I still see some fluff).