The continued dissolution of metal into the bleach will have some effect even if it is only the buildup of sludge. I would keep a close lookout for particulate matter and decreasing bleach activity with buildup of stain in white areas. Just be on the safe side.
I would find plastic substitutes as well. It almost seems like maybe there is a dissimilar metal electrolysis going on as well as a simple chemical action. If you pull the racks frequently and rinse them down do you have the same problem? Maybe part of the issue is a low grade stainles alloy.
What's the chemicals doing to your plumbing? Yikes!
Somewhere in the manual, it says that the developer and bleach/fix have to be mixed together before it's flushed down the drain. The opposing qualities of both solutions will neutralise each other, so what goes down is quite 'dead'.
Mine older kits not say that. In fact, the kits included small tablets that were to be added to the bleach to neutralize it as well as adding developer. There was a buffer difference between the developer and bleach that required extra alkali.