I was having the same problem, was going nuts trying to find out what kind of "bug" it was.. I spent 5 hours deadheading today, and then spraying for bugs, and the last few hours searching the internet for what kind it could be.. I just came across a forum that said it could be caterpillar "poop", and yes I did find one, on one of my 4 plants.. then someone asked could it possible be seed... ding ding ding!!! I think that is exactly what it is, because when deadheading, the stems that were dried out I clip off and they seemed to have the most black specks in them, and now I remember seeing some of the pods were actually burst.. So I am positive that is what it is.. black, shiny, hard little pearl shaped seeds about the size of a fleck of pepper.. :)