I'd get a new vet. Potatoes are poisonous (especially the peel part if it's green or sprouted) and mushrooms are a fungus, I don't believe mushrooms are poisonous to pigs but since they are herbivores, they don't eat fungi.
If you look on the second post on the Nutrition charts thread, you can see they are on the do not feed list.
Do NOT feed avocados, coconut (both too high in fats), iceburg lettuce (low nutrition, high in nitrites, high water), tomato stems or leaves, potatoes, rhubarb, taro, mushrooms, peanut butter, hot peppers, hot herbs and spices, dry beans and peas, nuts, jams, jellies, fruit preserves, sweetened fruit juices, pickled vegetables, coffee, cola, milk or dairy products to include yogurt, cake, cookies, baked goods, fried, frozen or cooked foods.