Brewed a batch of beer on July 25. Pinched yeast and airlock bubbled for about 10 days or so quite steadily. Then seamed like the fermentation slowed sown and had a yeast cake sitting on top. I decided to wait until it sank to the bottom before racking to my secondary. No worries just wait it out. About a week or so ago I happened to walk into my fermentation room and heard the airlock bubble every 10 seconds or so. I have it in a glass carboy with a towel on top so I lifted the towel and there were bubble and all sorts of fermentation activity going on. I've never had this happen before. My temp has remained at 66 plus or minus a degree or two. Any insights as to what is going on with this pale ale?