Did you happen to come from a different platform like iOS? I am using both an iPhone 6s and a Lumia 930 and I can confirm that even though the Instagram and new Facebook apps are direct ports, they are slow as hell and laggy in scrolling compared to their iOS versions.
Well, I don't find instagram to be laggy or anything compared to iOS. At least on the latest fast ring build. I don't use facebook so I don't know about that app.
