Well how about the kind of developer? I mostly use Rodinal, pretty dilute stuff. You use a pyro developer? Might be if I used your developer I'd start having that problem too and have to adapt. There has to be some real reason for it.
Makes me real curious.
Lately I've started using dip n dunk for my C41, I was getting a bit leery of the fill times for the tall tank as compared to the 3:15 developing time. Didn't leave much leeway. Besides that the damn lid always leaked and I hated how the bleach would dribble everywhere while I inverted the tank. Dropping the reels into prefilled tanks is so much cleaner!