Put 6 cups water, the lentils, beans, quinoa, garlic, carrots, celery, onions, bay leaf, salt, herb blend, some pepper and porcini mushrooms (if using) in a slow cooker. Squeeze the tomatoes through your hands over the pot to break them down, and add with their juices. Cover and cook on high until the beans are tender and the soup is thick, about 8 hours.
