I am brewing a Brown Ale which is about 4 days old now. After 12 hours, the airlock was beginning to bubble and after 24 hours if was bubbling once every 15 seconds. After about 2 1/2 days the bubbling has been significantly reduced and, from what I can tell, it may have stopped. That or I am just too impatient to wait around for it to twinge. Is this a problem, has fermentation halted. Fermentation began at about 72 degrees (which I thought was too high) and is now reduced down to 68 degrees. There hasn't been a whole lot of krausen, at the max maybe an inch. Now there is just a thin layer of broken up, non foamy krausen. Any ideas on whats up?