Before the winter period my avocado tree's leaves started turning brown. As time went on it got worse and worse. My largest avocado tree now has only 7 leaves left from the 22 it started with. My smaller avocado tree lost a few but seems healthy and has grown 3 new leaves back since. But my larger avocado plant hasn't started growing yet at all. I would really like to know what is wrong with my plant's leaves and how I can prevent any more from falling. I have checked on different responses but the way the leaves are browning seem different. Thanks.