I am a beginning DSLR user and am in the process of deciding on what lenses to get for a 400D to use in a similar situation as your gymnast shots. A couple of options are the Canon 85mm f1.8 (which I noticed you used) and the Canon 50mm f1.4.
Could you possibly indicate focal length, aperture and speed for the photos? Tired to check the EXIF but could not see it.
Did you use a flash on any of the photos?
Thanks for your help.