Dishwasher does work. But no heated dry and try to lower your water temp if possible.
Go to bricklink.com on the forums, there is a great amount of people who know how to clean lego, but be sure to get multiple answers, sometimes some people have odd and bad suggestions.
Don't know about the discoloration, havent had to deal with it to much
Only a M:Tron can fix something that isn't broke!