One thing to know about directional lights: it shines evenly in one direction only. It's light rays are parallel to each other as if emitted perpindicular to an infinitely large plane. (straight from F1)

From the looks of it, you have about 20 directional lights facing about the same direction. This is unneccesary since one directional light facing straight down with the right intensity value would be pretty much the same. I think you may want them to be spotlights instead and perhaps add a few ambient lights here and there at very low intensites to light the entire scene.