Yes, definately you need to get it up. What test kit are you using. I have to say it is rather HARD for salt water to have a pH that low.
Try using a different test kit to measure, or take a water sample to your LFS to have them test. How are the fish doing?
If in fact you need to raise the pH. You can use a buffer product which you can get from the LFS, or you can use baking soda. Raise pH very slowly, however, and take the reading during the day, at the same of day for accurate reading.