Recently, I took my vette out for a run and noticed that the brakes did not have their full stopping power and the brake light came on eventually.

The car does stop, but not as well as it used to and the light will come on and off at randomly. When I pump the brakes, the light does go off after a bit.

It is not leaking any brake fluid. Any idea of what this could be?

If you have the original brake calipers they were prone to having porous castings.They usually dont leak but will suck in air and cause your brakes to go soft and brake light to come on.All you have to do is bleed your brakes and they will be fine for awhile.Aftermarket brake calipers are they way to go.

Sounds like the mastercylinder is getting weak and worn. You might want to try and bleed your breaks just to see if you have air in the system. Remember to bleed from both bleeders on each caliper. I use a vacume pump to bleed my breaks. This makes life so much easyer. But to me it sounds like the master cylinder needs to be changed. Replace it, DON'T rebuild it....

The C-3 had a characteristic problem - primarily in back - with rotor runout. Essentially, excessive runout in the rotors caused the calipers to suck in air. Try bleeding the brakes, particularly the rear. If this helps, and the condition returns, you need work on the rotors. Good luck.