I am heartsick. Two months ago, I was given about a 2.5 foot tree/plant for my 68th birthday. I had wanted one for years but had never seen one in any garden center or big box store. Now, my sweet plant has black spots on the lower leaves and it seems to be working its way to the top.

I believe I understand it may be from a fungus brought on by overwatering, which I am dumbfounded because I watered it cautiously and sparingly. It sits in a bright south window. My husband ordered it from a mail order grower and when it arrived it looked healthy, glossy and unblemished. Is there any way to save it? How shall I treat the problem.

Will you please give me some advice?