I have a Jade 'tree' (4 feet tall, 4 feet in diameter) in an enormous pot, and it constantly loses leaves and sometimes branches. I cannot tell if its getting too much water or too little water (those seem the most common diagnoses for these problems). I check the dirt before watering, and it seems dry to a finger-depth, but I cannot get 'deeper.' I've been watering about once a month. The previous owner swore he only watered it every 6 months. Most of the leaves look plump, shiny, and healthy, but some look a bit dessicated. Please advise! I love this plant.