pH rises naturally due to CO2 (carbonic acid) loss in solution. You stated you keep your water for at least 3 feedings. Some of that water is going to naturally evaporate and the carbonic acid with it, hence you’re seeing a rise in pH.

My water is around the same and I always pH it.

I have 2 seedsman seeds white widows in flower along with a sweet seeds green poison. I also popped 4 purple lemonade FF from FastBuds about 2 weeks ago.