pH goes up when I put the plant in the rez.

If I am changing the nute solution, and I have the rez at pH 5.8. Then I put my baby in the res, and the pH jumps up to 6.7. Is it my hydroton? I washed it rather thoroughly before I used it.This is the third week, so I would think most of the particles have washed off. Is it because of my air stones? Is it the oyxgen? What's the deal?

7 gallon rez with 3 part GH nutes and ST.

Do I understand..Are your plants in the rez, or flood tray above the rez? Hydro? Aeroponic?

dmc hydro. plants are in the rez.

dwc* i meant

Try adjusting it more than just on the week change. As the plant drinks the solution nutrients are taken out which raises the ph.