When I kegged it, I added more sugar for carbonation (25g or so, boiled in water). Since then I've tasted once or twice to check on progress (only tiny amounts each time), the beer seems excessively sweet for the small amount of sugar which I added, carbonation doesn't seem to have occurred at all, and the gravity has dropped to 1.023 which is lower than I expected it to drop even when fully fermented out. Also, there seems to be a thin layer of krausen forming at the head of the beer inside the keg - about 1cm worth. There was no krausen in the fermenter when I kegged the beer. Should I be concerned about any of this?