Would you worry about municipal water at 8.4?
Not so much about the pH level, but maybe what's in it that makes it that high. Lots of Ca maybe. The Ca could build up in the soil and make the pH rise a bit. Too much Ca can also cause lockouts.
My well water is a little high. Around 7.8 or so usually with some Ca. My soil buffers it down to like 6.2-6.3 immediately.
But I do use a little citric acid sometimes to prevent the Ca from building up too much in the soil. It acts as a chelating agent to break bonds. I also add dry amendments that have Ca, so it's not all coming from my water.
Citric acid works great as an organic pH down if you want one. His Ca to raise pH should be fine too. But I don't think you need to use either.