PH issue? Maybe?

Why does my PH always go back to 6.2 - 6.3? I adjust it a couple hours after mixing nutes to 5.5 and by morning its back up. Can anyone explain this? Im growing in rockwool and hydroton with ebb and flow flood system. Feedings are twice a day.

Your plants take in different nutes at different times ( like more N than P for example,out of the water) and this can alter your Ph every watering. Don't fuck with it or you could have issues due to ph fluctuation.. balance your res daily and don't sweat it.