Adapting difficulty. Bug or a feature?

[Diktaattori]

I am leading my opponents by huge margin. Now all new landmarks I built have 1 or even 0 culture. Is this hidden adaptive difficulty setting that makes game harder when you are doing too well?

Edit: I don't have any mods installed and installation of Civ is brand new also

 

[jros83]

There's no such feature, but I doubt it's a bug. Did you ever find out what it really was?