This is a weird one. I brewed up my third batch, a honey wheat and bottled it about a month ago. Tonight I enjoyed a couple and before rinsing out the bottle I noticed that there are some strange, very dark patches on the yeast cake left in the bottle. It almost looks like mold, but not exactly. The beer tastes fine and show absolutely no sign of infection while in the primary. I followed the same procedure for sanitizing my bottles that I had with my first two batches, and I had great results with them. Any ideas?