Hi I have 20 Shared Photo Streams on my personal iPhone. The size is a cs. 300KB (Kilobytes). I have completely reset the iPhone to iOS 9.1 and set it up as new iPhone just to be sure, after a few hours the capacity decreased by a good 10GB while having the "shared" tab open in Photos -> so the Photos did download (not all! which is another problem). I have confirmed this on the iPad at my work and included a screenshot from it as well as from my iPhone. The iPad at work has 1 Shared Photo Stream of 50 photos so the size is for sure more than 8KB! Do you also have this problem?