Came back to normal mileage this week (~45mpw) after a BIG illness- induced down week (16 miles) but every single run I’ve gone on, including a tempo yesterday, my Garmin race predictor for the marathon has gone down a few seconds (gotten slower). It’s not significant (was at 3:16:11 at the beginning of the week and is now 3:17:00) but why does working out normally make Garmin think I’m getting less fit?