Wild BP swings in six weeks

Upon a reading for my physical this week, I have seen a 48-point drop in systolic (160-112) and 30 point-drop in diastolic (92-62) BP from my last reading prior to Memorial Day (US) I don't take any prescription drugs, my diet has been only slightly high in sodium, but nothing extreme, I don't consume refined sugars or alcohol, and stress and anxiety are close to nonexistent. Since that first reading, I have only lowered daily sodium consumption.

Given that not even two months have passed, is this a normal swing, or might the first numbers have been an error by the person taking my reading?