Which disk brakes? Original KH disks with 4 piston fixed calipers? 73+ disk conversion with single piston sliding calipers? Some aftermarket conversion?
Original combination valve? Distribution block from a drum conversion?
Rear brakes working at all? Drums still?
They sure can. Doing it equally on both sides is a bit of a trick though (but not impossible). Still if it’s both fronts equally I’d be looking at the system before it splits to start with.