Ficus benjamina, also known as weeping fig, drops leaves for a variety of reasons. It is extremely sensitive to changes in temperature or light conditions, and simply moving a pot from one part of a room to another can trigger leaf drop. Or a coat of fresh paint in your house near where the weeping fig resides can cause leaves to fall. Insects could also be the culprit. Are the leaves sticky to the touch? Is there webbing stretching across the tops and undersides of the leaves, and along the places where the leaves join the stems? Any of these scenarios suggests an insect pest. Take a few leaves-fresh ones that you pick off the tree and a couple that have just dropped-to a local garden center or cooperative extension office and ask them to diagnose the problem.
I'm sorry to tell you that your responses to the leaf drop-watering more and fertilizing-are not the best ones. Sometimes leaf drop on a plant results from overwatering. Roots die, then foliage begins to fall. Until you diagnose your plant's problem, avoid giving it lots of water or fertilizer. With fewer leaves to support, the plant needs less water and fertilizer.