....wait, didn't you say the tap was pretty good, and was 7.0? At 9.0, that's seriously bad, super nasty hard! I have doubts it's that bad unless you know you have brutally hard water, and were pH downing the hell out of it to get it to 7.0...? ... yes, I suspect the meter is off calibration,... do you store it in the proper solution, and have the calibration solutions as well? 7.0 and 4.0 specifically,... Until that gets figured out nothing you read from it should be taken as accurate,...
... trust the probe more --but never immerse it in liquids, BTW! --just making sure-
you're using Roots organic line? See, that even more weird for the pH issues, should be less likely to swing like this,.... leave the original ones alone if they're coming down soon,... Using the A8, are you taking reading after you have fertilized? This will give skewed readings,... the soil shouldn't be dry, or soggy wet when testing for best results,.... meantime, if the plants look OK, don't flush them,... check the pots again tomorrow, before feeding/watering unless they are that dry,... clean that probe tip with the buff pad, and wipe clean between pots,... something is TARFU, Jeff, and with a suspect ph meter, I can't say what's next,.. need tap water info, new pot readings, and depending on the water info, and meter recalibration we'll see about Ca-Mg/ flushing and all that,...