There is no need to waste any additional film, the negatives are your key. I would suspect that the milky, low contrast images are badly overexposed. The corresponding negative frames will appear very dark. If this is what you see when you examine the negatives, I would suspect that the aperture actuator on either the lens or the camera is not working properly resulting in the lens not stopping down for the exposure.
To test the lens mechanism:
- Take the lens off the camera
- Put the aperture ring at its largest f-number. The view through the lens should show the aperture opening at its narrowest.
- While looking through the front of the lens, flick the actuator lever on the rear. The blades should move from full closed, to full open. The action should be snappy and there should be no hesitation or sticking of the blades.
- Move the aperture ring to the next wider click setting and repeat through the entire range
There are other possible causes, but it is hard to troubleshoot without having the camera in hand. One thing you should check is the condition of the light seals and mirror bumper foam. The foam material disintegrates over time and can be the result of light leaks into the film chamber. To test the light seals, take a toothpick or a thin wood splinter and touch it to the foam seals that fill the light trap where the film door fits into the camera body. The material should be resilient and should rebound after pressure. It should not be sticky, gummy, hard, or crumbly. Similarly, there is a foam bumper that the mirror rests against during the actual exposure. It is at the top front of the mirror box at the front margin of the focus screen. It too should be springy and not sticky, hard, gummy, or crumbly. If not good, the foam material should be replaced.
Bad seals can cause light leaks. Bad mirror foam may result in crud being flung onto the focus screen and other internal parts. Seal replacement is part of the standard CLA (clean, lube, adjust) that most camera repair shops offer.
Steve