hi sometimes you get this from old powder that drops down from the soap box ,if you pull out the soap draw and check that it is clean at the back of it as sometimes the powder is not all flushed out. the other cause of some discolourisation of washing can be caused by a bra wire that as been pulled out of the bra and is rusting at the tip-these things can come out check if one is missing but they normally find their
way down to the pump and cause the m/c not to drain correctly and your washing stays wet as a result
Dave creda engineer (retired), November 2010