This chart below really shows what is happening with your nutrient absorbtion related to pH for hydroponics. Some nutrients absorb best out of range on both the high and low side. There is definitely no "perfect pH" but there is a range where you get the best balance and availability. I shoot for 6.0 but don't stress if it wants to run a few points higher or lower. A pH section would be a great addition to grow diaries.
https://www.opengrow.com/gallery/image/151262-gh-ph-chart/