Out of nowhere I cant use the white color at all for some reason

I literally cant color with white at all. Im cleaning a page and I'm trying to use white but it wont show up at all every other color on the spectrum works but white. However if I erase a part of a layer and try to use white it works but only on the erased area. I am using photoshop on the iPad and this applies to all my files. I've restarted my iPad, updated it to the latest version and still nothing.