I agree that your current method doesn't seem like it's working. People don't tend to react well to "punishment" styles of motivation. It doesn't stick enough.
If their laundry is in their own rooms, I say you make them close their doors. Their rooms are their domains. Those are the only areas they control. It is their one refuge. Their one sanctuary. Treat it as a separate country. They need to keep their doors closed on their country. The rest of your house is the way you want it. You can even put a fun sign on their door saying it's their own country
Let their country be the way they want it to be - it's the only space that is wholly theirs.