I've run Yosemite for some time now, this issue is recent. My assumption has always been that Time Machine autonomously overwrites old backups once your time capsule is full.
So my question is :
How do I resume normal Time Machine backups without having to manually erase old backups. I know I can delete files from Time Capsule
Time Capsule :
461 GB of 2TB available…backup error is
The backup disk needs 536.69 GB for the backup but only 460.78 GB are available. Select a larger backup disk or make the backup smaller by excluding files.