So i just developed a roll of Delta 100. It looks fine at a glance, but on closer inspection or under enlargement it can be seen that there is a large dark cloud through the middle of the roll. The sides of the film are look ok but it's just this large smudge straight down the centre that continues over the whole film. It's strange because I've developed a few rolls now and they've come out fine. This roll was developed with new batches of chemicals at recommended concentrations, temperatures and times. Does anyone know what I have done wrong? edit: I didn't use stop bath in between developing and fixing but I did rinse with plenty of water. Could this be it?