Doesn't need to be flushed. If it were me, I'd use it up til about two weeks prior to harvest, or stop if it causes any revegging or dark green too far into flower.
its fine its organic! but unless everything else youre using is completely organic than you need a good flush. with my experience unless i used ALL true organics ALL the way through i get the best results with just flushing with ro phd water. people like to get so fancy with their flushes and i never understand why. at that point you got what you got.. flush it out and enjoy