in my own experience, stimulant (caff, bronkaid, big ass coffees) and/or sinus season (causing equilibrium in head to get funky from the building up super sexy snot everywhere) can lead to things like this being off, just a bit.
it's good that we're aware of our bodies doing the small changes. Helps us avoid casually popping a 2nd, 3rd, 4th caffeine pill.