Grout can cause pH to creep up. Your fill water can cause it which reminds me. Many in here post water/chemistry related issues but I havent seen any fill water tests. Its handy to know what you are filling your pool/spa with.
Aeration will also cause pH to climb and is probably one reason some seem to think Ozone systems will do that. Its the aeration and another reason to go Oxy generated Ozone. Less airflow.
Keep the calcium up so the water doesnt try to get hard eating the grout. Keep the Alk a bit higher to try and lock in the pH tighter. Hopefully you add very diluted acid very slowly to prevent knocking the alk down so you aren't constantly adding bicarb which of course is an age old fight that drives people nuts.
This might be a good case for 2-sp. pumps to circ on low speed with no aeration during off times.