You've done some good troubleshooting, but multimeters are cheap and great for tracking down problems like this.
Get a meter. It is well worth it.
It sounds like both drivers have opened up, because if they shorted, I think you would have noticed the amps doing something about the short.
It is strange that they both went out so close to each other, but it could happen.
You've already checked for a loose connection inside the cabs, right? Like maybe something vibrated loose on the binding posts. Seems unlikely, but worth checking. At least do the battery test on the driver outside the cabinet.
"Still, a man hears what he wants to hear and disregards the rest." --Paul Simon The Boxer