So I've had a reoccurring issue with my last few extract brews. I'm following the instructions laid out with the brew kits exactly and make sure everything is very clean. My end results have been a very foamy beer when I first open and pour, but then the head settles out and it's very flat. Now, I can still see quite a bit of carbonation coming up from the bottom of the glass, but the surface doesn't show that. The taste is decent, but it's always too sweet and flat tasting. The most recent brews I have done are a dark coffee/chocolate ale, scotch ale, and a Shiner clone if that helps/makes a difference. Please lend me your collective knowledge.