Its quite possible that your crossfire setup got messed up. Make sure the bridge is secured, it might have been knocked off partially during transport, or like others have stated there may be a dust build up. Honestly the best thing I can think of for diagnosis purposes is to try with 1 video card and see what framerate you get, swap it with the other card and see what framerate you get, and then put both back in since if one card's fan is failing and overheating its going to affect the other.