S.F.
I would repot the whole plant. Sounds like fruit flies, so something in the soil has created a new home for them. But of course, fruit flies don't cause black spots so I don't know what that is.But new soil and a dry place would help. Just get new soil, and be careful not to damage the roots. If you are attached to the pot, make sure to wash it out thoroughly, and clean the area around where the plant was sitting...good luck!