What ph are you feeding at during flowering?
I like to vary my nutrient ph each feed keeping it in range of 5.8-6.3, not exactly the same every time during veg. Growing in coco you should lower ph during flowering.
When i see the chart showing the best ph to intake each nutrient, they don’t line up exactly at 6.0, some slightly above some below. 6.0 is generally in the sweet spot however the ph scale is not linear. It is more like the richter scale where 1 point represents 10x the strength so each tenth does make a difference.
If you are currently feeding at 6.0 and runoff is 6.5 I would feed at 5.5 ( no lower) and get the runoff to 5.6 to 5.8 during flowering.
My 2 cents-
Nice looking flowers-