i have 2 ficus, one about 2-3 ft tall and another one barely over 1ft and i have had some problems with them but they are still alive..
if there is a change in light intensity they tend to drop leaves.. if the light is too hot they drop leaves.. and sometimes they drop them for seemingly no reason at all but i have found if you mist you can cut down on watering because the leaves are getting the water from the misting.. i spray 2-3 times a day and water only once a week and my plants are doing pretty well except for my small ficus because i recently changer to a hotter bulb and half of the leaves dropped but i have rotated that one of the enclosure and its bouncing back somewhat.