Here's my opinion about it....Once INERT mediums, grow rocks, wool, etc, have been rinsed and are currently in use, IT SHOULD NOT, really be contributing to that problem...If I had to guess, your starting water is of a more alkali nature....Mixes typically like to buffer a little BACK TOWARD the waters starting pH...ALSO, plants in a rapid growth stage will make pH change...In that case, it's a sign of rapid growth activity...ALSO, how grower feeds can SIGNIFICANTLY make the pH change UP OR DOWN.....I am a light feeder compared to many, and my pH ALWAYS raises over time...Over time can mean in mear hours...Heavy feeding on the other hand will make the pH #'s go down..That is especially true during early flower when a high Phosphorus ACID is in the mix....That higher acid, of course will buffer the #'s down...When mixing flowering nutes, most growers notice that your pH WILL BE lower than mixing with their veg nutes....Its due to the Phosphorus acid.....
NOW, a pH drift to some degree, SHOULD BE WELCOMED...different nutes absorb at different pH values...chasing that PERFECT pH will drive you crazy...
I wouldnt be that concerned about how yours is behaving...YOU DO though, need to understand how it behaves and use that to your advantage......EARLY veg, my Hempy's CAN GET #'s higher than I am comfortable with...I have a small hole drilled in the bottom sides of my bucket (not the 2 inch high drain holes)...I have a rubber stopper in those....A cpl weeks after translating I will SAMPLE a little water that is sitting in the buckets internal reservoirs....Many times, It has creeped up to high 6's and even 7 s yours do....SO, I will flush heavy with a pH correct solution weak in nutes....After that, I turn right around and water with pH AND ppm correct solutions...Just resetting everything....SOMETIMES this isnt necessary, but sometimes it is....I DO understand that mine can do that, so I am prepared to make adjustments....
I ALWAYS feed every watering, but with moderate nute levels...plants enjoy that stability over those who feed, feed, flush type watering programs....This also keeps things less apt to build up or get deficient....Only make nute increases when they want it, not because any charts say they SHOULD need it by then...Not saying your over feeding, but keep things modedate and constant...UNDERSTANDING how your pH behaves will become very clear after a crop (2 at the most), IN THAT PARTICULAR SYSTEM...every system behave differently...Learns your well and dont chase smaller drifts...Maybe water with your pH slightly lower, let it drift up past IDEAL, and rewater when it starts getting too high...I.HAVE ALSO NOTICED all my pH drift (going higher), SLOWS WAY DOWN, once they are a 2-3 weeks into flower...That insane growth of stretch and transition into flower is over and MY pH stablizes much easier......
Hope this doesnt confuse you more than it helped, but you are not alone...pH drift is part of the game....A few variables are involved, but UNDERSTANDING HOW THE PH IN YOUR SYSTEM behaves is the key...Once you know that, you can deal with it, and they will be fine....Welcome a a small controlled drift though instead of chasing it...YT
