I think Mike meant it can't be that low....and I agree. If it really was 7, any aragonite sand you may have in your tank would be dissolving.
What brand test kit are you using to test the pH?
Here's a little test you can try. Take a jar full of saltwater from your tank and put it outside with an airstone bubbling outside air thru the water. Test your water and see what it shows.
Don't get caught up chasing pH and adding buffers. Depending on exactly what you are dosing, it could jack your alk
too high or add so much boron to your system your alk
test will give false readings. BTW...what exactly are you dosing to raise pH?