Auto layout isn't working as expected for laying out buttons?

I'm creating a scene in XCode in Main.storyboard where the user is able to choose between 5 options (buttons) and when I created the auto layout to horizontally center the buttons, as well as vertically space them 5 pixels apart:

On the 3.5 inch screen, the buttons take up most of the screen

On the 4 inch screen, the buttons take up about 3/4 of the screen

On the 4.7 inch screen, the buttons take up about half of the screen

It makes sense for this to be happening, but I created a @3x, @2x, and normal sized (1x) images using Prepo

The buttons have custom background image properties

How can I get the 4 inch, 4.5 inch, and even 5.5 inch screens on the iPhone to display like the 3.5 inch screen where the buttons take up most of the screen?