I have two mature lime trees and both are experiencing leaf loss. One is experiencing significant loss and the other has moderate loss. The area of loss seems to be concentrated on the back side of both trees. They are still producing fruit but the loss of leaves is alarming. I don't think the issue is due to over/under watering - I am watering them as prescribed. I fear that the trees may have either root rot and sooty mold disease. How could I confirm this and what is the remedy if there is one? Thank you.