that's not a significant swing, it should not cause much of an issue.
just to make sure you can try dosing twice a day, before lights out and in the morning.
can you add it in your sump and see if that make a difference? You are still going to have a concentrated swing of Alk/PH better to have the happen in the sump than in your display.
I would add it as far away from your return pump in your sump as you can get