From what I know about brakes, and pads in particular, that is indeed brake fade. With the front brakes providing the majority of your stopping power, I would agree that the front brakes are suspect.
I would guess that the pads that are installed are POS...OR possibly the front rotor(s) have become contaminated with something.
The brake fade comes is generally a result of the rotors/pads getting overly hot (sure you already knew that tho
. At this point, stopping power is reduced...so another idea is that maybe one or both brakes' pads are dragging while the brakes are NOT being applied and therefore generating heat....so then when you go to actually use the brakes for real, they heat-up THAT much faster and you see the brake fade.
As far as the brake pedal application....was the pedal firm when you saw the brake fade? or did the pedal continue to go to the floor? ....just reaching here...maybe the brake fluid is bad? water? bad master cylinder?
In any case, I don't like to screw around with brakes and play guessing games. Is this was me, with my limited knowledge of brake systems, I'd have it in the shop pronto.