I'm assuming from your original post that you are using mesh lights/emitters to illuminate the scene? It looks like insufficient samples, as the light intensity looks strong enough. Don't use the main render settings box, use D3D's in scripts>partners>dimension3D>render firefly. Use the IDL settings on the right hand side. Don't use the sliders, manually input the numbers. For example, the slider goes to 2024 samples, but if you put in 4000 samples, it uses 4000. Personally I don't use mesh lights much in Firefly because of the samples needed and the massive increase in render time. I tend to use point or spot lights. This scene is lit entirely by the skydome externally (so a mesh light). You can see a few of your pale splotches n the shadows on the left side of the image. Increasing samples was the only way to reduce them. Add atmospherics, this wasn't a fast render.