Hey all,
Phew, my rep stays in tact
! I agree that you should check runoff. We need to know if you are dealing with a problem there as well as the former mixing issue. The best way is to use distilled or RO water and simply catch the runoff and measure. The very first runoff is always much higher different than the balance. Its a good idea to catch the first bit and read just for knowledge sake. The amount of change can be an indicator to media conditions. The big key is to use a reliable meter. I've used a bunch over the years and the best one I founf is the Hanna "black". Near lab quality for around 150 bucks. You don't need to spend that much but at least be sure to calibrate often. Realize that the runoff number you read is NOT the exact number of the media. Typically, the media will actually be slightly higher than the runoff. ProMix is know for pH issues. You possibly are dealing with pH issues from the fronts.....improper mixing,inherent issue with media and potentially worsened by low pH nute adds. Doh! I suspect your runoff will be low but not ridiculous. Your now mixing nutes correctly but your media is saturated with the old soln. Flushing often and/or watering to excessive runoff will help to replace old with new. Be careful doing this as root rot can be an issue. Grower presence is the biggest asset you have.
Get the runoff number and lets wrap. Peace.