You won't get an accurate pH reading after bottling a sample of water from your tank and transporting it to your LFS. Once you take the water out of the system, the oxygenation ends and the pH will gradually drop.
Do you know what the salinity was of the water that was in the bag when you bought the fish compared to the salinity of the water in your system? The bigger the difference in salinity, the longer you need to acclimate the fish to your water by slowing adding your water to the water in the bag with the fish.
I dont but I use their water they mix (its a mom and pop store) its probably close. Im planning on buying a refractometer. No more surprises.