Photos can be problematic on a new topic. You can include it on a reply.

Can not see photos. You need to make sure they are not grayed out after adding them and submitting the post.

The Houzz app simply sucks when it comes to photos. It takes some patience and may be a few expletives to get through it.

This is a lower resolution image

And a lower resolution of the dryer lint screen

And a lower resolution of the dryer lint screen

definitely looks like something left in the pockets, or perhaps a hole in the lining and that is padding used like in quilted jackets? Is the stuff on the jacket loose or is it part of the fabric that's discolored? What is the fabric composition?

Do you use powder detergent? Although I’m sure you’ve ruled that out. Do you have kids who might have left craft items in pockets? Chalk, glue… just guessing here.

Were the white marks visible before washing? It could be mold or mildew.