iPhone won't automatically synchronise to iCloud

Hello,

For the past few weeks I have been having the same problem, my iPhone won't automatically synchronise to iCloud.

When I add an event to the calendar, add a reminder or a contact on my iPad or Mac I have to manually synchronise the app for it to apear.

For example, when I add an event on my iCloud calendar on my mac it automatically synchronises with iCloud so when I open the calendar on my iPad it's already there; but with my phone I have to open the Apple Calendar app go to my Calendars and pull down until the little wheel appears manually synchronising with iCloud. The same goes for the Reminders and Contacts apps. ALTHOUGH weirdly the Notes app synchronises perfectly.

What can I do to set it back to normal?