I opened the file this morning and found the background mottled. It's mottled over the sea as well. I didn't do anything but open the file which wasn't like this yesterday.
That's hidden by layer as a default, and it also doesn't look great with the effects turned off. Its a lot more subtle with them on if you don't want perfect paper ;)
Somehow a 'blood' sheet added itself to the map while I was playing with the settings