I think you are right about the loss of daylight. My 19 layers -- who will easily produce 7 dozen eggs a week in summer -- have now started their winter break. I don't do supplemental light during the winter, and they don't produce eggs. Until spring.
Some breeds will continue to lay during the winter but even my Sapphire Gems and Buckeyes slack off then. Although they are good for multiple eggs per week in summer, most days now, I get one or NO eggs.
Welcome to bYC, where you will find lots of people willing to talk about poultry all the time!