Yes, it's most likely the temperature then. Ambient temperature has a huge impact on feed consumption. If the previous batch was running around in spring temperatures without any supplemental heat then they were definitely eating a lot more than if they were kept in a brooder with supplemental...
It's most likely environmental factors. Short days means less feed consumed. The same goes for warm temperatures. If this flock is still being kept warm in a brooder versus the last flock that may have have had brooder lamps turned off earlier then that may account for the reduced consumption.