I had the same problem with my outdoor plants!Look closely at your leaves and their underside and you should notice a little round black spot!Scrape it with a knife or something and that should take care of your problem for that moment,Then what i did was...I took some garlic and few chili peppers and i mixed them in a blender and then i added 2 tea spoons of antibacterial dish soap or somekind of soap in there and put it in a one litter bottle and left it for 24 hours,I sprayed all of my leaves and their undersides too and the problem disapeared

You try it it might help you too