I don't see it and gets too blurry when I enlarge it. If you are concerned about it then put some antifungal cream on it every day until you see it get better or if it starts to get worse then stop. Be sure the top layer of substrate is dry while treating.
My baby tortoise grew black blotches that looked EXACTLY like that and it freaked me out too. Over time it just became a beautiful black design on his plastron. So yeah even though it looks very scary at the begging, as long as it keeps symmetry I wouldn't worry about it. Although if there is any crustiness I would definitely treat it with a little cream as Wellington said. And the white squiggly lines im pretty sure is actually a sign of good hydration, although I may be wrong about that.