First of all, don't get discouraged. I think you are going to discover that the greatest difference in your speed and the others is paddle stroke efficiency. If you get a chance, go to a forward stroke clinic and really practice what they teach. Soon you'll notice that you are paddling faster with less effort. While the standard paddling norms that are taught are quite correct, you'll begin to discover personal nuances that work best for you. It's also worth learning a repertoire of strokes that you can vary between to give muscle groups a little recovery time on long paddles.