Many aren't laying this time of year. Those older ones that stopped to molt generally won't resume until December to March depending on breed, and overall production. Young ones will lay at a decreased rate throughout winter with some breaks.
Hormones are dictated by increasing or decreasing light. Under decreasing light hormones wane. The original intention of egg laying is for reproduction. We have bred birds that will continue to lay throughout the year, but the the natural cycle does still persist. After the winter solstice daylight will increase, and hormones will start to rise again. Those that are in a good enough condition should resume laying.
It's taxing to produce eggs constantly. So many take breaks, especially during colder weather as reserves are used to stay warm.
It's important to make sure your birds continue to consume enough water during the cold months, as eggs are mostly water, and a decrease in intake will affect production.
Some people add extra lighting to bring birds back into production faster. It probably isn't as successful on low production hens, but I haven't done it so I'm not sure.
