I made a near 6 gallon wort. Sanitized everything meticulously!!! I left it overnight in a glass carboy to cool down ready to pitch a starter slurry the next day. No yeast was added yet when I came back to the wort the next day it looked like a full fermentation was going on, thick thick mess on top of the beer, large globs of white stuff in the wort, looking also like curdled milk in parts. It also smelled sour. Could this be a bug in the dme? Or an air infection, acetobacter? I did syphon the wort previously a few times back and forth into a separate carboy as I dropped my beer thief (fully sanitized) into the carboy (twice!! I know, very clumsy of me). Any ideas? Thanks very much.