[Z-linkCobra]

I would say your calipers are sticking. Not so much the pistons in the calipers but the sliders. Some years back when I was running the dragster quite a bit I started experiencing a soft pedal in the brakes. Right when I would stab the brake the first time it would almost go to the floor...pump it one time and had plenty of pedal. As the day prgressed and the temp rose the brakes would start to drag a little. We ran 6 piston Mark Williams calipers with a solid plate(no sliders). What I found was a slightly bent mounting plate causing deflection of the rotor. Thats when the rotor and the caliper are not inline with one another.

Dont know what kind of caliper mounting plates you have but make sure they are lined up properly. Heat will warp things in unusual ways and have you chasing your tail.

Just something from my past experiences.