I collaborate with my color lab that develops and prints color negatives. Lately we have some problem with film developing: we have some dark streaks on the sky, especially when the sky is a large and smooth zone in the frame. Or maybe we note it only in these frames because they are smooth, altough not all the frames have this problem.
I don't understand what causes this developing problem, so we use a professional giant vertical chassis machine in which films are vertical and change automatically each bath with timer. Chemicals are obviously fresh.

What do you think?

Thank you