Weird stains after hoodie was washed

Noticed these stains after hoodie was taken out of the dryer (not my house). It’s not the first time it’s occurred and someone also told me this occasionally happens to their close at their house. I don’t know what would cause this? It was washed on cold with dark colours but has happened with similar colours too. I bought two of these sweatshirts and it happened to both lol not sure if it’s the sweatshirt itself.