Also consider adding some supplemental light. Daylight is great, but in winter, there just isn't much (either in intensity or duration) where you live. Doesn't have to be fancy grow lights... a full-spectrum LED light, 12 hours a day, may be all the boost you need.
You nailed it Roberta.
When I had my GH in NH that was my biggest mistake. I had some supplemental lighting for winter but it wasn't nearly enough.