PH a little low is normal if lights are out in the tank, or you just took reading when you woke up in the morning ect. Buffering PH is normally a band-aid. The actual cause might just be the natural daily cycle of flux and your timing when you tested.
Keeping your Ca and other major elements stable should push and pull your PH to where it needs to be. Within 7.6-8.6 I wouldnt worry, just retest at a few different times of day. If low, then first check your Ca, bet its low too. Adjust it first and all will most likley work itself correct JMO