The problem is the stabilizer or final rinse you used for sure. I don't have water marks on my films and I don't use a sponge. I only hang my films to dry in my bathroom. I use Kodak chemicals and that of course includes Kodak final rinse.
I like Kodak Portra 400VC medium format (220 mostly) very much. This is my all around national parks film. With quality processing this film's grain is very decent despite people bad mouth a bit about its grains. The colors of 400VC is plenty beautiful to me. It's the best film for me on sunny days. I think I am talking about the older 400VC, not the latest that is related to 400UC.