I brwed my extract bitter four weeks ago, its still in the fermenter. This is my 4th overall batch, and my 2nd of this kind, so I know what it should look and smell like. About 1 week in I noticed some weird spots floating at the top, it almost looked like a off colored mold. I noticed as well that the krausen didn't look like it did last time - not as big, long lasting, or thick. I smelled the wort probably a week ago and it reeks. It smells like old olive juice or something. I'm suspecting very heavily that I have an infection, but I don't want to dump it all out without being sure. Can anyone give me some info on whats going on here?