I think your answer may be in what happened to me a few months ago, but first I want to say that PH should be going down, not up.
At any rate my Ph was going down unusually fast, and so I added PH up, several times... and by the time they were done, they certainly we not looking right. It turned out to be my ph meter. PH meters are very sensitive things (so I've learned), and the bulb needs to be kept moist (wet) and clean. In may case I was doing that, but it turned out to be the PH meter.

SN
SpaceNeedle Reviewed by SpaceNeedle on . PH ACTING STRANGE DOES ANYONE KNOW WHY MY PH IN MY NFT SYSTEM IS GOING DOWN AND NOT UP, IT HAS ALLWAYS GONE UP FOR THE LAST 8 YEARS OR SO, BUT THIS LAST SIX MONTHS OVER 3 GROWS HAS BEEN GOING DOWN. I DO CLEAN MY SYSTEM AND THE PLANTS ARE GROWING AND LOOK FINE. BUT I READ IF ITS GOING DOWN AND NOT UP, THERE IS A PROBLEM, I HAVE CHANGED NUTRIENTS ON THIS GROW BUT STILL THE SAME AND THE WATER IN THE TAP IS STILL AT 7PH SO I DONT THINK THAT THE WATER IS FUNNY. ITS REALLY WEIRD. Rating: 5