Brown stains left behind on laundry after washing are usually caused by pollen or plant sap.
Stains on delicate summer clothing: pre-treat the stains with a detergent enhancer before running the wash program. Leave the detergent enhancer to work for 10 minutes. Then take note of the care label and wash the garment accordingly. Please use a delicates detergent and detergent enhancer as well.
Stains on white or colorfast clothing: please use some additional powder stain remover during the wash cycles and select the highest wash temperature permitted by the care label.