Are you using the regular range pH test? This is only valid up to about 6.8, and will show 6.8 even if the pH is really higher.
Test using the high range pH test. This will test into the 7s, and a bit higher, if I remember.
I do add co2 and there is driftwood and dirt so I guess that could lower it. But it seems like that is a very low pH for such a high KH. I have your regular API test kit with test tubes and solutions and what have you. The pH test is almost impossible to tell the differences...seems like they're all slightly varying shades of blueish yellow. Just did the high range and it turned a lighter brown than the lowest reading of 7.4. So I guess it's possible it could be higher than 6.8....just so hard to tell the difference in color.