It could also be scanning issues. Back when Costco developed/scanned film, my scans would look great when this certain lady was working. When it was one of the other doods, they would often come back muddy, scan lines, sometimes scratched!
I asked her about it, and she mentioned that she was really careful when she was handling film and scanning. In comparison I saw one of her coworkers literally drag a developed film roll across the floor on his was to the scanner..