I recently brewed a one gallon red ale from extract and then a few weeks later a 5 gallon chocolate milk stout. The red ale kit came with sugar drops for carbonation. This beer didn't car well at all, seems to "fizz" quite a bit, almost sparkly. It had little if any head retention, which I know isn't uncommon for a red ale, but still it was disappointing. Also, it has this slight tart flavor up front and a hard to describe faint sour-like odor, almost like the way a beer can smells the day after drinking it. I used some of the same equipment for my stout and I cracked the first one open tonight. It carbonated much better using the priming sugar instead of fizz drops, however, the "stout" itself seems to be on the weak side. It's not a porter, but it just doesn't seem to have that heavy body characteristic. The chocolate is noticeable, but not very strong. I also noticed the same sour odor and faint flavor as I did with my red ale. I soaked the cocoa nibs, some cinnamon, and vanilla bean in vodka for several days before adding to secondary. Both of them are "drinkable", just not something I'm keen on sharing with friends. What infection does it sound like it contracted? How would you go about preventing it in future batches?