iPhone 6 photos not syncing completely with older devices

Hi,

I have an iPhone 4 and an iPad 3. When I take a photo on the iPhone it automatically syncs with the iPad and vice versa. Now, I've bought an iPhone 6, everything synced but the photos. Altough, if I take a photo with the iPhone 6 it syncs with iPad. but the opposite don't happens.

What should I do?

Thanks