Flushing?

More than just rinsing, I recommend gradually reducing the fertilizer doses until you're only watering with water. About a week should be enough; you'll notice because the plant starts consuming the nutrients from its leaves, and that's when the leaves will begin to turn yellow. At that point, the plant will be ready for harvest, and you'll also notice it consumes less water. Washing roots is something very extreme, and there are also products for "washing roots," but I would only use both in case you're using mineral fertilizers. If you notice, it's impossible to do something similar with plants that are directly in the soil. Cheers!