Sure, if you want. but what do you think it accomplishes? (rhetorical). By diluting whatever is in the medium, it doesn't change the constitution of the flower already grown. there is no excretion system for such things and running a bunch of water through rootzone doesn't flush the plant. It dilutes the medium and that does impact how much nutrients gets absorbed but doesn't do anything for an overfed plant, directly... the excess has to be used up to drop it to safe levels in leaves.
so, if you think it is overfed and the concentration of nutes in medium is too high, definitely get a little extra runoff... that's a matter of cause and effect, but dont do it to 'flush the plant of minerals' because that's not possible.
also, wouldn't adjust your harvest due to this fact.. if it is ready, do it. That should simply be an observe-and-react behaviour.. while an individual may have an opininon of what is best, your trigger is not an opinion. Experiment with early-middle-late harvest and choose what you like best, then stick to it.
fwiw, plant isn't overfed. Any blemish could easily be chalked up to senescence. I wouldn't bother flushing, but you could definitely give a normal irrigaiton with plain water if you want to save the hassle of mixing nutrients. The leaves have plenty left to give.