You can run plain ph'd water up to two weeks at the end of your grow.....I would start flushing the BB at the normal time (perhaps with plain water and no flushing solution) and just continue to run them both with ph correct water until they finish......again......you can keep the WW on plain water for up to two weeks before harvest so hopefully that will be enough finish time for the WW. I personally dislike the taste AND the way the weed burns when I don't flush it......tastes metallic and very "crispy" and "overdry" (too many salts? )