I made a lot of improvements in iCloud Sync in the last few updates. So please make sure you update to the latest version 4.0.5.
If the changes contained changes to audio files, pdf and midi documents, version 4.0.5 will most likely fix those.
If not, please send me the log files (via Settings > Create Support Email) of the device where you made the edits. And of the device that did not sync. And mention the name of the song and what exactly you did edit.
Oh and keep in mind, that the changes might take a minute or two to be received by the other devices. iCloud Sync is not exactly real time.