will the ph level increase over time as more water changes occur?
your pH is likely fine - the test strips are giving you an incorrect reading. pH can be affected by the ambient CO2 in the air. This is one of the reasons why we let out water sit for a while after mixing - to achieve an equilibrium.
this is a good read on Ph by @Randy Holmes-Farley and. a quick quote:
"In my opinion, the pH range from 7.8 to 8.5 is an acceptable range for reef aquaria, with several caveats. "



