Reminders no longer syncing between devices

Hi,

As the heading says, my reminders are no longer syncing between iPhone 5, iPad 3 and Mac 2011. I'm signed in to the same iCloud account on all devices, and my iPad and iPhone both have Reminders sync turned on in the settings.

Anyone have any idea about why this might be, or how to fix it?

Thanks, Steve

(It's also not always reminding me with a notification, which is a bit irritiating, and last week I had to delete duplicates that appeared on some devices - is iCloud a bit broke?)