So i've updated to the latest version being: v3.9.0
After doing so, all my players on the server lost their existing balance.

Is there a way for me to get them their balance back?

Thanks in advance.

It's always recommended to back up before updating anything, but having a back up would be the only way to recover.

There wasn't anything that changed with the data handling though, so I'd need to know more about your configuration and plugins that utilize this plugin.

Edit: I did tweak the limit handling in the latest update, though unsure if that was the issue.