Q.ficus benjamina raised from a little slip is sick
My ficus is dropping leaves and appears to be dying. I have raised this tree from a slip and she is now 20 years old. An inside tree with plenty of light, and I prune her occasionally because she is 5 feet tall and full. Many of the leaves falling are brown, but many are green and fall off at a touch. Please help, this tree has been with me through thick and thin and is like a member of my family.
Do you fertilize very much? Have you repotted very often? If yes to the first, and no to the second, I'm almost sure that your ficus has elevated salt level in the soil. Even if you don't fertilize, and you have repotted, try this to see if it helps. Try leaching the soil - that means to run a lot of water, about 5X the volume of soil in the pot, through the soil and let it run out the bottom of the pot. It will wash out all the salts, and your tree should start to feel better in a few weeks.
The other thing is to investigate the moisture level of the soil in the bottom of the pot. It may be staying too wet, and over time some root rot has got in there. Pull the plant out of the pot and inspect the roots. If you see any black, brown, or mushy roots, trim them off, wash old soil out, and repot in fresh soil. This article has some information: https://www.gardeningknowhow.com/plant-problems/disease/treating-root-rot-gardening-tips-for-housplants.htm
Make sure you test the soil moisture all the way through the pot: https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/testing-moisture-in-plants.htm