This problem cropped up only a week ago and it only happens when I develop two 120 rolls in a large stainless steel tank. I've done this before dozens of time with no problem but only last week I noticed on the bottom roll dark patches running parallel to the bottom edge of the roll relative to how it rests in the tank.(posted 8293 days ago)The patch seems darker on the part of the negative that sits on the outer part of the reel and less apparent on the part that's further in the middle of the reel.
Just for the record, when developing two rolls of 120 I mix the delveper and pour it into the empty tank - turn off the lights and roll the film onto the reels -- slowly lower the reels into the tank -- turn on the timer and start aggitating. When the developer is finished I turn off the lights again -- pour out the developer and hold the tank under running water for two minutes allowing for five complete water changes before pouring in the fixer and turning the lights back on.
Any ideas on what's causing these patches? Could it be because I'm not using an acid stop bath?