High PH

[SAMSHUNG]

Nearly two months running my aquarium with all my parameters looking good. Then today I decided to check my PH (API) against the PH reading of a used PINPOINT PH monitor that I recently purchased from the classifieds to see the difference between the two. The API read 8.7-8-8 !?! Typically it hovered around 7.8-8.0. The PINPOINT gave very erratic readings which I'm assuming is due to the probe being old and dried out.

Measurements have always been taken at noon and nothing was introduced into the aquarium accept Seachem Kanaplex and Focus to treat two clowns. Also I don't know if it would have that much of an impact or not but the Chaeto that I've been cultivating in the DT to mitigate any blooms while cycling has grown quite a bit. It now occupies a good 1/5 of my DT. Could this have that much of an impact on ph?

Basically I would like to get some insight as to what has contributed to this unusually high PH and what might I do to safely lower it.

A thousand thanks to all who can help this amateur out.