You are not really supposed to put knives in the dishwasher. The rust spots are probably caused by the detergent damaging the finish and then water + metal = rust. We hand wash knives.
Also make sure you don't leave tomato sauce on silverware in the dishwasher. This will also eat at the finish and eventually ruin your flatware.

We had tomato chicken stew so maybe the tomato did it! What a pain to have to wash the knives separately. I had 5 knives in the dw and only one came out with rust spots. Thanks for the info.

I never put knives of any kind in dishwasher because of the rust spot reason. It's said that the joint/seam at handle and blade of dinner knives is vulnerable too.

lazycook

I have had the brown spot problem with my Kitchen Aid. It only happens with silverware that has mayonnaise on them. Now I wash the mayonnaise off before loading. I hope this helps.

I answered this question in May. If you want to see the post; do an appliance search on "brown spots"; it ran May 13th.

I have put my flatware knives in the dishwasher for 40 years and have never had a problem. I do hand wash my good cutting knives. Some of the flatware is over 30 years old.

I never noticed mayo, but def tomato sauce, etc. (Why it doesn't affect forks and spoons I don't know.) I periodically use Barkeeper's Friend on them; it gets it off but it does come back.

My flatware knives occassionally have this happen too...I think for me its due to the fluctuating iron content in the water where I live.