If you had some significant temperature drop between when you took it off the EVSE and when you started up the next day, maybe, but that's a bit more than I would expect.
The main battery should have minimal capacity loss over time. While the 12vdc battery, like most lead-acid types, will self-discharge, but that's not what you are measuring.
My experience is that the SOC doesn't change much over time while just sitting there, but that the range estimate can, mostly based on temperature, while just sitting there.
There may be something else going on that may explain your observation...it may or may not point to a problem.
2011 535i x-drive GT, 2014 i3 BEV