I have a similar issue, only mine is the blue. I have had yellow background before and I HATED it. Still not entirely sure how I got it fixed, and like a lot of problems it comes and goes. I know I did have developer leakage from the seals on the developer tubes having disintegrated. That's not the problem this time around, though. Already gave the blue developer rolls, and all developer rolls, a scrub down. Didn't solve the issue.