BA6 - Major frustration

So after coming home from the media lab I wanted to have a look at the scene because before I left I noticed how the end walls and the gravestones towards the back are much lighter than the rest of the scene and for past 2 hours I have been trying to figure what is causing this and can't find the solution, I have literally tried everything, from the lights (which I definitely think is the issue) to the textures, I'm going in tomorrow though 8/05/13 to speak to the tutors to see if they can help me figure out a way to fix it.