I have a Heartleaf Philodendron that was my first real houseplant (I now have 47). It has absolutely thrived for the past 3 years. For the past 2 months, it has been dropping leaves like crazy. I probably pick 3-4 yellowing leaves off a day. It’s lost almost all of the bigger leaves. The center of the plant is almost completely bald. The vines look ok though. I moved it to the window in the picture about a week ago. It was on the small stand in between two windows in the picture below for at least 2 years. I’m not sure if I overwatered it or if something else is going on.