I doubt root rot is / was causing your ph to rise .
Rot more often than not causes drop , not rise . I use hydroton too , I soak it in ph corrected water for 2-3 days before even introducing it into my system , and I rinse as much of the powdery crap out of it beforehand . Depending on what stage of life the plants in I get as much as .5 or more ph fluxuation per day .
I try to keep my res. somewhere between 5.5 - 6.2 . Hydro is much more maintence than soil .
Peace
Crispi :jointsmile: