PH Spike

I see an autopot like feeding system? So, the rising pH is due to the nutrient solution getting warmer. Also, if you are circulating the solution 24/7 with the pump, it will quicken the pH rise via warming and airating the solution. Put a timer on the pump, it is enough to stir the solution every few hours. If you want to aerate the roots, autopot has the airpot that is put at the bottom of the pot and it is fed air via an airpump. It is worth the hassle. Good luck, and consider investing potassium silicate, stronger plants and a good pH buffer/ can be used as pH up. If you decide to add silica, you can take some of the potassium of the other feed/nutes off to compensate.