Diagnosing Sudden Alkalinity - Is this normal?

[tang daddy]

Something to note, when I had higher po4 my tank used less ca and alk and as soon as my po4 dropped from .24 to .06 the corals started growing faster and alk had to be readjusted... why not use some buffer to get the alk slowly back to where you want it and then leave the 2 part to maintain it.
You can mix some sodium bicarbonate to your ato so it adds little amounts everyday to bring it back to 8.5.

If you have lower phosphate, alk at 7.5 is totally fine. I keep mine at 8.5 right now as I like corals to grow faster.