rhodes68answered grow question 4 years ago Give ya my best here lets see...
At that PH target any downward variance, and these pens can vary .3 easy, you are in trouble with Phos and CA which can cause problems at the top of the plant looking like light burn in ways. CA and Phos have a REAL close relationship in flower.
If she were mine I would up the PH to center of the range, 6.5, so if it varies a little things are still cool.
In particular important on soil where you wont add anything to change the PH for days.
Good luck