I would have to say that's a testing error. It's almost impossible for a saltwater system to have the pH that low. What brand test kit are you using?
I see your in PA, so at this time of year the windows are closed tight, which can raise the co2
levels of the air in the house. Higher co2
levels can lead to a lower pH. You can try pointing a powerhead at the surface of your tank to help promote gas exchange and if you have a protein skimmer you can try running the intake airline on the skimmer to the outside somehow to get fresh outside air into the system.