I had these 'strange' streaks and other 'things' appearing, not always, on my home developed films, B&W and/or colour, long time ago.
Unexpectedly, I found the remedy in the ledger of Kodak's Q Lab System, at the time when I did the E-6 processing at home (in the ever lasting Colenta).
Therein Kodak advised against touching the emulsion, AFTER exposure and BEFORE developing, with your bear hands/fingers.
And yes, with this in your mind: when unrolling a roll film and separating it from the backing paper, one is tempted to touch/slide a finger over the film in order to have the paper and the film roll up separately and then to tear the tape holding the film.
And then, again, to unroll the film to load it on the developing reel.
Actually, it's somewhat nearly the same as what causes the strange thin black lines appearing on the sides fo the roll film (120 film): pressure fog, but here by your finger(-s)...
It might appear on 35mm film also, why wouldn't it?
So, NEVER EVER touch image part of the undeveloped film emulsion with whatever it might be: fingers, clamps, the flanges of te developing reels (metal or plastic), the sides of the film itself, the film holder in the camera, just NOTHING!
Hold the roll by it's sides/ends and never stress it!
A pair of cotton gloves could be you best friend, yet 'unhandy'...
PS: sorry if my description isn't that clear, translating, in my head (and with Google translate), from Flemish in to English what I was trying to say, isn't always so obvious, but I hope you can "see the picture"...