Doug,
A higher TA will result in a faster rate of pH rise, depending on the source of sanitizer you are using (some are more acidic than others). So you generally want to adjust the TA to the level where the pH is stable. If that's at a lower TA, as in your case, then so be it. It's perfectly fine to have the lower TA.
If one needs to get the TA very low, say to 50 ppm, for pH stability because they are using hypochlorite sources of chlorine (bleach, chlorinating liquid, lithium hypochlorite, Cal-Hypo) then one can additionally use 50 ppm Borates for pH buffering (say, from ProTeam Gentle Spa, for example).
Total Alkalinity (TA) is not only a pH buffer, but a SOURCE of rising pH itself due to carbon dioxide outgassing which is faster with at higher TA, lower pH and with more aeration. It's counter-intuitive, but it's a chemical fact.
Richard