All three pedals are separate and not related to each other. It is strange that all three pedals loose pressure.
Accelerator: There is a cable like a motorcycle cable going from the accelerator pedal to the throttle body. There is a spring at the throttle body and one under the pedal that is responsible for how much pressure is needed to press the pedal. These springs provide a constant force and the pressure will change if one or both break. If that happens you will know for sure and the pedal will sit on the floor.
Brake: There are four components that determine brake pressure. 1) Brake booster, 2) Master cylinder, 3) Front caliper cylinders and 4) Rear wheel cylinders. Oh yeas and the flexible hoses to the wheels.
1) Brake booster can fail in two ways. 1) a torn diaphragm within the booster and 2 a damaged vacuum hose from the manifold to the booster.
2) Master cylinders usually fail due to failed seals or damaged cylinder liner. In both cases the brake fluid will leak either into the car or into the booster.
3) Front caliper cylinders fail either due to failed seals of rust within the caliper causing it yo seize up.
4) Rear wheel cylinders fail the same way as front wheel calipers.
5) Wheel brake hoses become damaged by the inside hole becoming closed. We call it collapsed hose. This situation does not allow brake fluid to return back to the brake reservoir. You can feel it by the brakes hold the wheels even if you are not pressing the brake.
All 1 - 5 will have a effect of the amount of brake pressure you put on the pedal. Which of these 5 problems is with your car I cannot tell sitting here.
Clutch: There are a few reasons for clutch problems. In your car there is a cable just like the accelerator cable going from the pedal to the gearbox. Generally there are two adjustments. One is at the pedal and the other at the gearbox. I am not sure if your car has both or just one. Anyway, with the foot off the clutch pedal, there should be a free play on the clutch cable at the gear box end of about 5mm - 8mm. Clutch pedal pressure depends on three things, 1) The spring at the clutch pedal, 2) the spring on the clutch throw out bearing mechanism and 3) the spring fingers on the pressure plate. If your clutch pedal pressure is more and the clutch is engaging right at the end of the pedal travel it means the clutch plate is worn out and become thin. Thin clutch plate means that the angle of the spring fingers has become such that more foot pressure is needed to separate the plate from the disc. Best way to destroy the clutch is to drive the car with foot on the clutch all the time. If long life from the clutch is needed, the foot goes on the clutch only when the gear needs to be changed or coming to a stop.
