The plant is dropping leaves because of some environmental or cultural stress. They grow best with bright light and you indicate that it receives light all day. I can't speak for NY weather, but here in the midwest we've had lots of cloudy days. Also, any window treatments such as drapes or sheers cuts back drastically on the amount of light that comes through. Is the plant near a window, door, heating vent? Places such as those can have drafts that are not good for the plant. Watering can be another issue. During winter, plants have reduced watering needs because house temperatures are generally lower and light levels are reduced compared to the out-of-doors. It's okay to let the soil dry before watering. Powdery mildew can be another possibility. It is prevalent with many indoor plants because of cool temperatures (if you keep the temperatures low or if the plants are near the window). This disease is easy to identify because you will see white powdery growth on the leaves. Unfortunately leaf drop is a very generic symptom that can have many causes, so it's a matter of eliminating the possibilities. If I had to pinpoint one problem, it would be lack of light.
