Runoff ph kind of high....

G13 Pineapple Express auto , NLxSkunk 3 weeks into flowering.. In gallon pots 4x4 rockwool cube filled with hydroton.. Watering with 5.6 ph , 1/4 strength solution a about 780ppm. Runoff coming out at 6.2, 6.4 ph.. Can I ph down the solution and use it again????

Hi Rem
Doesn't look anyone had a view on your dilema.
I have some experience in an Ebb n Flo system.
Even if you doing a top feed it should be the same.
I always recycled the nutrients kept in a res (tank) and usually had to ph down every 2 or 3 days.
I changed my nutrients every week altho i think i could have gone for 2 weeks.
No problems, I have now gone back to soil, so I can go visit the gran kids for a few days without worrying about pumps or clogs.
Good luck

Keep watering with 5.6. If runoff doesn't change after a couple weeks, then you got a problem.

You pre-soak the cubes?