Day #11 Bad Fermentation :(

I went to check on my sauerkraut like I do everyday and it has a layer of mold on it! :( I'm not sure what I did wrong. Maybe I let too much oxygen in? I know I didn't let it ferment too long because it says online that it can stay out for weeks...Either way I'm super bummed that it didn't work out. I took a photo of my sauerkraut after mold had formed...