First, if you already haven't, try disconnecting and turning off the sub.
Second, looking at the manuals for the various versions of the Dreadnaught, it appears that some modules on some versions have a switch on the rear to select between the balanced and unbalanced inputs, and some don't. It is claimed that the switch is not necessary on the modules that don't have it, but I don't necessarily believe that. If you are using modules that don't have a switch, you may need to connect a jumper between pins 1 and 3 of their XLR input connectors.
To do that, you would need a short piece of solid (not stranded) wire, that is of sufficient gauge to fit snugly, so that the connection is physically secure. Obviously, have the amp turned off while you are inserting the jumper.
Also, the Dreadnaught's manual emphasizes that it is imperative that the AC safety ground connection of its power plug not be defeated, for performance reasons as well as for the usual safety reasons. If by any chance you are plugging it into an ungrounded (2-prong) outlet, using a cheater plug (a 3-prong to 2-prong adapter), that could conceivably be causing or contributing to the problem, particularly if the adapter is not connecting the safety ground pin on the power cord's plug to the wallplate screw.
I don't think that the use of 24 gauge speaker wire, btw, has anything to do with the problem, although as you realize it is certainly non-optimal sonically.
Regards,
-- Al