iPhone 6 plus stopped uploading Photo's to iMac Photo's or iCloud

Hi, about 3 weeks ago my iPhone 6 plus on iOS 8.3 stopped syncing photo's to iCloud or the Photo's App on [latest Yosemite] iMac. I also have an older MBP with Yosemite and that is showing same as iMac which suggests iPhone may be culprit?

Any ideas?

I do love my Apple gear but ever since Photostream the whole iCloud Photo thing just hasn't worked consistently for me.

Regards

Matt