I transplanted an avocado tree a few months ago in a large pot about 2' in diameter and 2' tall with 4 different kinds of soil. The pot has holes in the bottom so there is drainage but it is dying from the top down. It has been inside for the winter and outside for the summer. Should I put rocks in the bottom to help drainage? What's the best soil? It's about 2.5' tall. How can I save it? Thanks for any help.