I looked at your blend, and the only excuse I can find to why they look weird is that the planes are only 2D, meaning they have only one face, and one normal. When a normal is facing outwards, it blocks light/rays from going into it, but if it is backwards, then light can still go through that side outward, causing those ugly black marks in meshes when your normals are reversed. Your Up/Down plane is pointing left, and the Left/Right plane is pointing up, letting light shine through to your top right, and bottom left cubes, causing the lightin problems. You could easily make the Planes into 3D objects by extruding them, even if my just a hair. I think this should fix your problem, thought I could be wrong…
Hold on Tight,
Edit: JSYK, this is the only seemingly possible quick explaination I could think of, and I didnt even try it, but, if it isn’t, post again, b/c is may very well be a bug. Have your tried other procedurals, like the one spin used?