Same here. My problem made no sense to me, either....but, for whatever reason, my soil mix ended up spitting out runoff water that was 4.0! My tap water is around 7.5, so I had always been pH-ing the water DOWN to get it in better range. But when I started to do runoff checks, I could see that something wasn't right. I had to start pH-ing my water UP after that and flushed several gallons of water that was at around 8.0, until I started to see the runoff test was finally starting to move. After I got it to around the 6.5 range, I backed off on the pH UP and went back to my regular routine. So far, every subsequent runoff test has been looking good and stable at around 6.5 and the plants have definitely bounced back.