Slate + style = performance drop ?

Hi,

I just discovered the stat function in the console, so i can be more precise.

In the first screenshot, all my widgets are collapsed. You can see a fps around 100.

Second screenshot, the main menu widget is on, that makes 6 buttons, and already the fps drops to 40.

Then, third screenshot, i switch everything on, and the fps falls to 5.

My UI, even unfinished, is quite heavy, i would expect a slight drop, but from 100 to 5 ? And even from 100 to 40 with 6 buttons ?

Maybe i am doing something wrong ?
I have been following this tutorial:

Any advice welcomed, as my UI is supposed to contain much more things, which obviously can’t be done the way i currently do it.

Thanks

Cedric