I don't think balancing will help, since I believe the files are not related to what is being stored in the cluster, but most likely temp and log files. You can try the following to try and find which files are occupying the most space.
run at the root level du -cs * | sort -g which give an output of folders and their file sizes. Go into the folder that has a large size and run the command again until you get into a folder where you can isolate which file or set of files are occupying all the space.
Hope that helps.