Above or below a certain point appears to affect different things with a mid line where most important nutes are available for uptake. That's always been true with chemicals in mfg, so it is with us closet growers. We found that all chemical composition must take into account where it will be used as the vehicle for dispersion is local water.
I'm on well water in a large farming community where all major plants (cotton, beans, corn, maters) are good with our ground waters but it isn't very good for cannabis. Weed just doesn't enjoy a below 6 ph for sure in my area.....so I adjust to benefit that one important factor. Seems 6.4-7.0 has been my best ....last time I had a stunt was with below 6 ph.