I have had a similar experience, except we were going 45 MPH (on my electronic speedometer) on a 10% hill when we needed to stop quickly.
Both rotors were smoking hot. If you had fade from overheating it will be a long decline that you were trying to go down slowly by using the rear brake or a panic stop from high speed with a heavily loaded tandem.
If you could smell the hot brakes it could be water that was absorbed out of the air by your brake fluid, or a low boiling point fluid.
Either way, flush the fluid and replace it with fresh fluid. Castrol SRF is quite expensive, but it has the highest boiling point of any DOT fluid I am aware of. This will also result in any air in the lines being removed if the job is done properly.
If the fluid is high quality and not contaminated, you might get larger calipers that will work with your SRAM setup,,(Hope makes some). They will make that Castrol SRF fluid look cheap.
Last edited by DangerousDanR; 03-15-22 at 04:15 PM.