What you are tasting it the primer that they put on the atty before it's shipped, I've had some that were a little sweet, others that tasted kind of burnt. It'll take a day or so for that to completely burn off normally and then your carts should taste more like what they are supposed to. If you have some
e-liquid, you can put a couple of drops on the bridge (the part of the atty that sticks out when you don't have a cart on it) and the will help it go a little faster. Or you can clean them in hot water and it will help that go a little quicker. (Check the
threads about cleaning an atty)
When you change from one flavor of cart to another, the taste will linger for a little bit too, so a lot of people have separate attys for different flavors or clean their attys whenever they change flavors. Me, I just enjoy the blend of the two in most cases. Menthol and cinnamon are the exceptions that I've tried, I have separate attys for those as they stay in the atty forever.