I keep getting these giant streak marks down my negatives after self development. Any one know what I need to fix this issue?
Are they on the actual negative as well? Do you use squeegee?
You can try and see what you get when you simply invert the rgb tone curve (or each of the r, g and b tone curves).
You can also share one of the negatives files for us to try. Use a sharing platform like google etc.
I did use a squeegee, but I cant see the marks on the negative itself.
Yes, I have tried that. Maybe the marks are really fine on the negative itself 
I personally think this is processing error. The lines are too straight to be caused by a squeegee. Is it on all of your scans or only one of them? If the whole strip of negatives has it on the exact same spot, then it’s definitely processing error ie camera/scanner etc.
The marks are consistent on the set of negatives. I’ve used 2 different cameras and the same outcome. I have been scanning with transparency glass so wondering if that is being picked up with the straight line marks Only one way to find out!
How do you scan, with a scanner? That might be an issue as well.