Check the bottom of the potting soil. It could be sitting completely saturated with water. Eventually the roots of the plant will suffocate, rot and kill it. The potting soil could be full of rot and fungus, so you will need to repot it with new soil. Also, if the dying leaves are all on the bottom shaded part of the plant it could be "self-pruning". The leaves that are not getting enough light eventually die off, but the leaves that are getting the light at the top are taking over most of the photosynthesis.