if the water runs out of the cup before it hydrates the soil your only getting the edge. try submersing your cups in a bowl an wait for the bubbles to stop. once a plant gets to a wilting point one of two things are happening to much or not enough h2o. you should be past any dampening off problems. deep drinks are better for leaching anyway. drain the cups after filling to remove salts an depending on how often you water as to how often you will need to feed