I believe on the bottle of Florakleen it says to use it for 1-2 days before harvest. So you'd give your plants just plain water for a few weeks (since you're in soil and there's some amount of nutrients in the soil, too), then add Florakleen to your water, maybe the last time you water. I'm not familiar with postponing harvest based on the PPM of the runoff, so I'm not sure what I'd recommend on that. If you've been giving just plain water for two weeks I think you should be good. As far as how long to wait after the last watering, I'm not it makes much difference except the longer you wait to harvest, the less the buds will take to dry because there will be less water in the plant. So if it's really humid where you are you might want to wait a while and let the buds start drying on the plant, and if it's dry where you live you might harvest immediately after watering just to help them dry as slow as possible.
