galen is correct. Patience is key. Your low TA will tend to bring your pH down. How high is your pH and how low is your TA? One thing you want to be careful of is very high pH because it will draw the calcium out of your water and create a sandpaper effect on your shell and plumbing. Baking soda, because it is a weak base (pH 8.6), raises your pH in a gentle way.
If you are not too high with pH you may want to let it set and see if it comes down.