Is it common the VO2 to drop 2 points down in the first week of Garmin Coach for half-marathon guided trainings?

I have been doing running trainings by myself in the last months. I had some VO2 max improvements, but once these were getting harder to achieve, I started Amy’s half-marathon training. In this week, the first of the plan, my VO2 max has dropped down 2 points. I’d like to know if this is expected.