Why are only some of my notes backed up on icloud?

[iMore Question]

I have an iPhone 4, version 7.1.2

I have successfully backed up my, contacts, calendar & reminders, but only SOME of my notes backup to my iCloud a/c.

All the notes were made after I set up my iCloud email a/c.

It backs up recent notes & even one from May, 2014, but notes around the middle of 2014, are not backed up.

A solution would be fantastic..... THANKS

Lorraine