Soil and Watering

After three years of "successfully" tending my trees, I thought I had the soil/watering thing pretty well under control. During the summers, all my trees did very well. Each fall I carefully watched the temperatures and when nighttime temperatures reached 55 degrees, I would bring the tropicals inside.
Although there was little in the way of leaf drop, there wasn't much growth. However, they still looked great.
This fall, after bringing them in, I noticed the Ficus Green Island didn't look very happy. It's leaves were looking a little yellowish. However, it was pumping out figs like crazy. By January, it had dropped half of it's foliage. By the middle of February, branch dieback became apparent.
At this point I decided it was time to look at the roots. When I lifted it out of the pot, the root ball came out intact. It did seem a little dry, but the roots looked fine and smelled healthy. I covered the rootball with a wet towel and prepped the pot.
Then I began carefully combing out the roots. This was when the problem became apparent. Ninety percent of the roots fell off with the soil. All I was left with were the larger roots directly at the base of the trunk. I finished repotting my sad little ficus in 50% grit 30%turface and 20% pine bark, all carefully sifted. I used this mix so I can water very frequently. I use only rainwater for all my trees and fertilize with Miracle-gro. No fertilizer for the patient until I see marked improvement. My diagnosis: I have been letting my tropicals get too dry. This took a toll on my Ficus Green Island. More on my experience with soils and watering to come.