First of all, there should typically only be one or two wires on the negative battery terminals. One will go to Chassis Ground, and the other (if it exists) would often go to a sensing circuit in your RV.
All of the other wires should connect to the Positive terminals of the battery.
As to your discharge problem, it looks like the previous owner had a problem himself, so it's hard to say what your problem may be.
One of the wires on the positive terminal is to the RV's Converter (Charger) which keeps the COACH batteries charged. So, make sure this is operating properly before you go chasing your discharge problem.
Then, I would check that EVERY accessory and appliance that runs on 12-VDC is working properly before moving on.