Dexcom sometimes uses to read low for me in the morning, too. But this discrepancy is more persistent than just the morning. Currently (it’s noon) I don’t have my meter, but the Libre is reading 3.8 mmol/L and xDrip is reading 6.1 mmol/L.
I think this sort of thing has been happening consistently since I started using the Libre and resulted in many falsely treated lows.