maybe a bloom booster?  i'm doing the flora series and I incorporate the liquid kool bloom during flower as per feed chart.  i'm not a hydro guy, but do grow in coco, just thinking 6.3 might be a lil high for hydro?  i do 6.1 on the upper limit and the plants love it.  I just double checked hydro ph nute chart, and it does appear that 6.3 would make Phosphorus unavailable.  which at this stage of your grow would be bad.