It looks like you're using the Mac Finder to view the images. Mac Finder has a known issue where it uses a hardcoded blacklevel instead of the one in the file (so if the true blacklevel of the raw data is different from what the Mac Finder is expecting, even if the blacklevel metadata is correct in the DNG, it will appear with a color cast like this). Try actually opening the DNGs in Photoshop/ACR or Premiere.