You've caught some good action here. As you've already guessed, though, they could benefit from tighter framing/cropping. They also could benefit from shallower DOF - both by getting closer to the action (or letting the action get closer to you) so the action fills more of the frame - and by using a wider aperture. That's going to be a real challenge with a manual focus lens but right now the backgrounds are a bit of an issue.
Thanks for sharing!