Recently updated the iOS app and it's definitely got quite laggy, especially on the pots screen (I only have about 5 pots too). Used to be so nippy as well.
I made the adventurous mistake of upgrading my main iPhone to iOS 13 and the Pots screen just refuses to load - tapping the icon freezes the app. As I keep most of my money in pots, I didn't have any money until I got out an old phone and installed Monzo on it.