I obtained a set of 32 used DT spokes. I built them up in a wheel along with 4 I had on hand. One of them broke within the first 50 miles and a second broke within the first 100 miles. Both broke in the center. You only see this type of break when there is a defect in the wire generally an inclusion. I have found several entire wheels full of spokes with this type of defect. I should mention I volunteer at the coops and have worked on hundreds of wheels. Most of the spokes with this type of defect are generic low magnetic stainless steel with no markings on the head. DT also uses a low magnetic stainless steel. If they are counterfeit I expect they come from this company. I will keep the public informed if they are any more breaks with a comment on my flickr account.
https://flic.kr/p/2gC4GDL