The detergent contained compounds (zeolites) to aid water softening which are not soluble in water. These have ended up on the laundry.
Try and remove the residues with a brush once the laundry is dry.
In the future, wash dark textiles using a detergent which contains no zeolites. Liquid detergents do not usually contain zeolites.
We recommend Miele products for thorough and gentle cleaning of your laundry.
