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?