Duplicate notes on iphone

I sync my iMac notes with iPhone/iPad and all of a sudden (worked fine for ages, 1 to 1 sync-ing) I now see multiple notes on my iPhone and iPad of the same note I have created on my iMac. I suspect the duplicates ior extra notes on my iPhone/iPad are created each time I've amended an iMac note? This is very annoying - anyone have any idea how to fix?