Zorachusanswered grow question 4 years ago If you aren't already, maybe try a Calcium Magnesium solution.
Also, I wouldn't trust the 'pH Perfect" as 100% accurate. Perhaps you have really hard water.
If you know somebody that works at a brewery, bring them a little jar of your nutrient solution to test the pH. You can also get cheap testing kits at the hardware store, but they are hard to read and less accurate.
Happy 420!