Q: iCloud calender

I Have two iPads and two iphones all share the same Apple id ans they are all running on iOS 8, yet when I put an entry on one iphone or one particular ipad it does not sync across all devices . I have checked all the iCloud settings in the devices and switched off and restarted the calender switch in iCloud settings . Is it possible I have added too many devices to my Apple ID and the iCloud server cannot handle it or is there some other problem?