1) you're running higher and 80 feels lower bc your body has adjusted to running too high or 2) you're dropping quickly or 3) your meter can run +/-20% of a plasma value and still be considered accurate
I was running high the last 2-3 weeks due to sickness... So yeah.. That makes sense.
I feel you. I'm in the exact same coming-out-of-a-cold phase and 70s felt AWFUL yesterday. Over treated and jumped back up to where I had been for days.
Resist the urge to over correct and your body should adjust to being in range again. <- easier said than done, but best of luck