I would not “flush” anything out of your soil. By doing that you will dilute or possibly kill your Beneficial microbes off and possibly introduce a ideal environment for root rot, or aphids. Dilute your nute solution down a bit Growing in soil is quite different from rdwc, if you do not add any nutrients this week at 300 ppm your plants will surely turn yellow in the next ten days. In my experience, soil grows shouldn’t go below 900 ppm using the 700 scale. Ppl can argue til they turn blue in the face but that’s what works for me. Chances are your tap water comes out close to 200 ppms. You will definitely hear different things from different ppl. You have to dig through all the information and find what works for you!
Good luck