This is a bit odd but whenever I do a whites / lights wash the clothes come out smelling fresh and clean. When I do a dark wash with the same washing powder on the same setting (40 degrees) it always comes out smelling musty and not nice and clean! Why is this?! It’s always the same! My machine is clean and as I say the light stuff never smells musty, so why does the dark? Should I use different washing detergent for darks or something?? Has anyone else had this?!