Ph anomaly - rises up in 24hours perioud

I don't bother checking pH in hydro DWC setups anymore as I try to keep as much Carbon access out of the growing solution as possible, growing strictly mineral..or rock salt, or the commercial general hydroponics three part mix.. the plants in this setup can easily regulate their own pH when left alone between water top ups and at the same time as the top up I check the ppm as well.. watching the plants leaves and vigor can tell you when the existing mix is getting too old and might need a fresh mix.. In veg hydro my ppm is 400ish, in late veg early flower it's at 600ppm and I bring it up to 950-100mid flower and late flowering my ppm is at 1150-1250 till fresh water flush for 3-5days to finish..

Your pH will most likely increase gradually anyway but that's a huge jump much too quickly. Easiest possibility is that you haven't done a full res change in a couple weeks. In that case, do a full res change and give it another go. If you've changed your res recently, then it's most likely a nutrient issue. My guess would be underfeeding. If your ppms/EC are dropping as pH rises, just add more nutrients. This, I bet, is what's happening. If your EC is remaining steady, it's a bit of an odd situation. Raise your EC if its below 1.0 and lower it if it's above 1.4. If none of these things are the case, then you have a nutrient issue, likely due to mixing in the wrong order causing some gelling. A full res change must be done again and make sure you give the res a really good stir after every addition. Stir in both directions to really get a good distribution.

Forgot to mention that in this grow I use a good ph meter and not some amazon crap.