UI images turn white when entering playmode

Hey guys!
I was making a Souls-like game and it was going pretty well, but now I messed up the UI.
It used to look like this:

And now it’s like this:

When I open the project it looks good but when I enter playmode all the UI images turn white. (Even the ones on the enemies). It’s like the sprites do not work.
Does anyone know how I could solve this?

This happened to me when I forgot to assign images in the inspector. Could this be the problem?