Spanx Simplicity strapless slip with convertible clear straps size Medium

Spanx Simplicity strapless shapewear slip with convertible clear straps - 28” top to bottom, 14.5” across top of bust, 19.5” across waist and 14” across at hip. Only worn once and washed - noticed some discoloring on body of slip but it has been washed and air dried twice! Definitely clean and must be marked from water or laundering? Women’s size Medium