I have a large, well cared for and suitably potted and watered and fed, ficus. Over the last week (while I was away) it appears to have become “Ill”. It has a great deal of dead leaves still on the plant and a large amount of dropped green leaves. The soil is still moist. The one factor that changed is temperature. The apt has very large tall south facing windows. It can heat up. To counter this I left the A/C on low. But it was quite cool in the apt upon my return. Not sure of best course of action now.
It is not unusual for Ficus plants to lose some foliage when their environmental conditions change. This plant is known to be very sensitive to light so if lighting conditions change, you can expect it to drop some leaves and produce new ones that will be accustomed to new conditions. This, however, doesn’t seem to be what has happened in your case, in which the light conditions remained the same
Leaf loss such as you describe in Ficus benjamina can occur when conditions are too dark, or too drafty, or too dry. It is intolerant of cold, and should be kept away from drafts. It is possible that your A/C changed the typical conditions of your home, creating more air circulation and drier conditions than your Ficus was accustomed to. This, coupled with the cooler temperatures during your absence, may have been enough to cause some leaf drop of green leaves. You are obviously doing everything right in terms of siting your plant in what appears to be bright indirect light. Consistent watering – regularly while allowing the soil to dry out between waterings – is also an important factor. Is it possible that it may have been watered too heavily before you went away? If the cause is environmental, your Ficus should begin to leaf out again.
It is always good practice to check the leaves and stems of your Ficus for evidence of insect pests, some of which can also cause leaf drop. Here is a previous Toronto Master Gardeners post that will help to identify scale insects on Ficus benjamina.