I have had my schefflera bonsai for 14 years. It has been a thriving, leafy tree the entire time. It is watered regularly and fertilized when called for. All of a sudden, it is dropping leaves, notice the branches are withering, the leaves that are left are rolling, drooping and the veins are pronounced. I have lost at least half of the leaves. There are no bugs or anything on the undersurface of the leaves. There are no roots coming out of the bottom, so I assumed it isn't root bound, although it has never been repotted. The soil is damp and it is not ready to be watered. I was away for 12 days and my thermostat was lowered to 56 degrees. Could it have been the temperature causing this?