Flsuhing was a good call. Did you check the pH of the runoff as well? You need to be certain that the soil is about 6.7, and also feed lightly with a complete grow fert mixed weak.
I would get to where you see healthy new growht, and regenerate your mother plant from clones. Start a few, and keep the healthiest ones. If she was flowered in that same pot, you are sitting in old sour soil and it's going to be a hassle keeping her healthy from here in.