The whitespots could be dust in the camera that had attached itself to to film surface blocking light and hence, causing white spots on negatives or black spots on slides.
Streaks may be caused by scratching the film surface. This may be due to again, dust on the film pressure plate or the pressure plate being not smooth. Scratches may also be the fault of the lab processing the film. Check the film surface carefully to see if they are scratches. Check also to see which side are the scratch then you would know if the scratch had came from the pressure plate. BTW, I had a GR1 a few years back that scratch slides but not negatives, returned it for another one.
Sometimes, it is the film emulsion itself that is at fault. I had experiences of blobs of black on Provia 100F before.
Note that dust on the lens will never show up on film. No lens is ever that close focussing!! A really dusty lens will only have a lower contrast as it will be more prone to internal reflections.