Ok, second question. Have they ever worked right? Or is this a new trailer?
If new, I'd just bring it back to the dealer and let them fix it. Too many possibilities there between a short, being mis-wired, etc...
If they used to work, then that confirms it's a short. Since it's affecting all the tanks, I'd say it's either directly behind the panel, or in the panel itself.
I haven't pulled the panel out myself, so I can't guarantee how easy this is going to be, but I'd start by removing the panel and first visually seeing if there's anything there, like a mice nest or something that might have chewed up the wires. If the wires look clean, and if they can easily be disconnected, I'd disconnect them from the panel and then check for continuity between them. Don't use the black tank for this test since the black's easy to still have something between the probes. I'd use the FW, if it's affected, since that's the least likely to have something on the probes.
If there's continuity, but the tank's empty, then most likely you have a short downstream on the line. That would be a bugger to fix so again I'd look to have a dealer (or the Reps at Goshen if you're going) take a look at it.
The most likely cause though, is a short in the panel itself. If the wires don't show continuity, that points to an issue in the panel. Again, a visual inspection for debris, fur, etc.. that can cause the short would be the first step. If it's clean, then most likely it'll have to be replaced.
Of course, as I said, I haven't done any of this yet so I don't know for sure what the panels look like on the inside. Hopefully somebody who's pulled one before can hop in and provide their feedback.
There's no use crying over spilled milk, unless it's on your keyboard.