I looked at your floor plan, and see that you have two washrooms. It is possible you have two black and two gray tanks, as that's how I'm set up on my 2011 35K with a bunkroom washroom, so five tanks including a galley tank. And to keep the sensors clean I just do a good long rinse until the water is coming out mostly clear.
Dave in SK
Trailer: 2011 Cedar Creek Silverback 35K
Truck: 2006 Dodge 2500 TRX4 Cummins
Seasonal at Saskatchewan Landing Provincial Park