The problem is obviously NOT the water heater, since the cold water is worse adn it never goes near the water heater.
It sounds like the source has compounds in it that you need to filter out prior to it entering your camper.
I would suggest getting a charcoal filter in a canister and hooking it up inline prior to the water entering your camper. The canister and filters can be had at Lowes, Home Depot or any of the Big Box stores. I would follow this up with a Camco in-line filter to complete the filtering process.
The charcoal should filter out the problem chemical or compounds and the Camco Filter anything not taken out by the charcoal element.
2012 Wildcat Sterling 32RL
2008 Chevy Silverado 2500HD LT Diesel
2001 Cougar 281 EFS (sold)
1973 Layton 23' (sold)