you did not add any new live rock or corals, perhaps something fell into the tank? happened to me a piece of rock I had on top of tank fell in and my numbers went bad.
Would like to come and look at tank perhaps over weekend? If it is usable for me will leave a sizeable depoist, does tank have to be moved right away. I ask because it would take at least a week for me too get people together and to rent a truck. if you want call tony 646 645 8215 .