ARD just showed a voter movement analysis. Greens won 210.000 votes from SPD, 200.000 from CSU and 140.000 from new/nonvoters.
If the Greens won 200k voters from the CSU, either CSU has gained some votes from other parties (pretty unlikely?) or CSU -> AfD voter movement has been more limited, with a lot of non-voters opting for AfD. Which doesn't seem to be an unreasonable idea given that this happened in the federal election too.
ARD just showed some of the figures for CSU. They lost 200.000 to Greens, 180.000 to AfD and 180.000 to FW. 210.000 voters were gained from new/non voters