If acros are growing, great, dont chase dragons! Might tweak a couple things like reverse light cycle between refugium and tank to try to even out the pH where its at. Id still crack the window a 1/4 inch or so to run the skimmer air intake outside for a couple hours to see if it changes, if yes, find a permanent solution, if no change, no worries. Can use a towel or something to create a thermal/pest barrier to the outside while you're ruuning the skimmer test. Also if multiple test give you a very close answer and one is way skewd, it is probably wrong. Electronics are not infallible, and there may be probe error, interference from a close by source, or something else of that nature. I know its expensive, but if you had another pH probe or meter, you could replace/or drop it right next to the current one to double check as well.