ok, i just spent some time on RC chemistry forum because i have never heard of high pH with a calc reactor. i found almost no mention of it there as well. one thing that might me going on, is elevated alkalinity which is causing your pH to rise. what is your alkalinity?

also, i have always heard that those pH sticks are not very accurate, and when is the last time you calibrated the pH monitor?

if you dont have any calibration fluid, do a quick test on some RO water with TDS of 0 and make sure the pH monitor says it is 7.0

you can add seltzer water or vinegar to bring the pH down, but make sure it is elevated before you do that. the seltzer is supposed to be safer because vinegar can encourage a bacterial bloom.

i have been told by matt that dust from new calcium reactor media can skew alkalinity testing, so maybe it is effecting your pH testing as well (just brainstorming here)