To clarify, I'm not talking about treating the entire wheel - merely the cracks. And here, I'm going to have to disagree with Sailor. Some recommend salted or unsalted butter, some oil or wax, even lard.
On taking another look at your cheese, I agree with Sailor that the mottling is due to uneven cook, somehow - some curds have experienced greater syneresis than others, usually due to uneven cutting, or hot spots - which can happen with not stirring enough. The mottling is actually causing physical ridges and valleys, which I didn't pay enough attention to on my first look. The mottling I'm talking about is an even, fully knit surface, but some patches of white and more yellow coloration may show up. I don't usually see this out of the press, but will see it at times after 24 hours rest in the cellar, before brining.
Something like this - hard to tell, but you can see a yellow/white gradient in places on the Parmesan wheel.