Do you happen to have a 2-roll tank? Or were these 120/220 rolls?

I have found that by using stainless reels and tanks rather than plastic ones, I have less contamination. I have used the same tanks for b/w and color(c-41) at school, just giving them a good scrub with HOT water after to make sure they're totally clean of residual chemistry, especially stabilizer/photo flo.