By “plain water” do you mean distilled, R/O, or tap/spring? CheersFrom that photo you have three maybe four weeks left. And don't drown your plants by dumping gallons of water through the pots. You suffocate the roots and you don't flush anything out of the plant. If you're in soil then plain water at the end. If in coco or some other inert medium taper back to 1/4 strength nutrient solution.