I started doing some brewing for the first time yesterday with some Cooper's Mexican Cerveza kit. Instead of putting the typical cover on the bucket, I was advised to take a garbage bag and seal the top while my beer brewed. Thats what I did. 24 hours later, went to check my bucket up, took off garbage bag, and stared in horror at light beige patches on top of the beer. Is this normal?! Can bacteria infest my beer in so little time? Or am I mistaken and everything is normal? The garbage bag may have been in contact with the beer while it brewed.