Do i need to P.H. down?

Not going to make a difference that late in a grow. TBH, if you have put the time in to fine-tune your nutrients you may just want to leave it as is. Will a slightly lower pH produce slightly more mass, all other factors the same? PRobably, but it won't be any major amount that you'd notice. A statistically significant effect does not always mean it is a large effect. You may have to re-tune your fertilizer formula if you shift pH. Probably not too much, but still a PITA. IS it worth 3-5 more grams per small plant? 1-2 grams? This is probably the range of effect and possible exaggerated. Ususaly the studies for this stuff is comparing total plant mass, so it's more leaf matter, more stem matter, more flower matter.. and flower is only a portion of the increased dry weight of plant mass. Look up some studies that are behind this concept. See just how much differing pH impacted plant mass compared to control group... consider how large the plant is, and think of it in terms of percentage. it won't be a huge number except when compared to pH ranges that common sense behaviour would avoid. 6.8 is fine. Oh, and this is just to flush.. yeah doesn't matter at all. Flushing only slows the plant down and no reason to do so at end of a grow cycle. So, whether its optimal ph or not it doesn't matter. If it makess you feel good, go ahead and do it.. the negatiaves are not to big of a deal, either, but there are no positives in that context.. just starving a plant and misunderstanding how plant biology works.. those minerals are stored in leaves, not sex organs. flushing does not change the mineral context of flower. Not a debate