Product review (5 stars): Silver turning dark from your Miele dishwasher? Problem solved
I have an old Miele dishwasher G851 SCI.  I also use silver as my everyday flatware.  I know some of you are thinking why but I always have and always will use all my "good" stuff.  My family has never thought twice about eating off of silver.  A few years ago I noticed a black sort of tarnish developing on all my silver after I ran it through the dishwasher.  Bear in mind I had always used silver so I thought it was something wrong with the dishwasher.  Miele is great about servicing its machines so they came out and repaired everything from the gaskets to the door seals,and hoses, etc.  They admitted they had no idea but thought maybe the rubber was breaking down and only depositing this darkness on the silver.  Everything else was fine, no dark spots on glasses, plates or pans, etc.  Miele also recommended I use their dishwasher detergent which is specifically formulated for Miele and costs 5 times as much as dishwasher tabs from Costco.  I used the Miele detergent for some time and it was better but not perfect.  I would polish the silver and then run it through and it would have this dark finish on it.  I called Miele several times and they blamed it on the new formulations for dishwasher detergents.  They said there was nothing wrong with the dishwasher.
One day, my son decided he wanted to change his usual breakfast meal.  He no longer wanted nutella and bananas.  Guess what happened?  NO dark film on my silver.  So the culprit is NUTELLA.  There must have been enough Nutella on the knife and on the plate to leave this film and for some reason the silver metal interacted with the hazelnut spread to cause a dark film to occur only on the silver.
Moral to the story...rinse your NUTELLA if you eat with a silver spoon.
I hope this helps others who may have experienced the same problems.