I fertilized it this year (Miracle-Gro Liquid Indoor Plant Food), which I've never done before, but it grew much faster this year which I was happy about. maybe that is causing the spots? The new growth has these little black splotches and I can't figure out what they are. I wouldn't be too concerned about just trimming off all the affected area if that's the right thing to do, but I don't know if maybe I should treat the plant with something. I water it every week or so through the warm months and less in the winter. It gets partial sun and it seems to enjoy it.
Thank you very much for your help, I really don't want this plant to die. It was started from a leaf pulled from a now dead plant that belong to a family friends plant that was originally his grandfathers! thank you all for any ideas you may have. it does seem to be spreading slowly to cover a larger portion of the leaf area, predominantly on the underside of the leaves.
