Every TM backup takes 600MB
You are likely running an application or applications that back up their entire database anytime any change is made to the database file. Microsoft Outlook is famous for this. VM Fusion, Parallels do this as well as any number of non-Mac applications.
To find out which application might be the culprit, I suggest that you use a utility like BackupLoupe to find out exactly what is being backed up on each backup pass. Once you have run several backups, it will be easy to find the large backup file and then Exclude it from backups.
To Exclude an item from a backup.......
Click the Time Machine "clock" icon at the top of the Mac's screen
Click Time Machine Preferences
Click the Options button
Click the small + button at the bottom of the Exclusions list
Use the Finder interface to navigate to the file or files that want to Exclude
Click the file to highlight it
Click Exclude at the lower right of the Finder window