Malnutrition - Conure

My green cheeked conure was acting so weak and sleepy so we took him to the vet today and found he has malnutrition. The veterinarian felt his breast bone and ribs. They were literally skin and bones. He weighs 60 grams (what should be 68-73 grams) and is fed Wild Harvest Super Premium Parrot Blend (it has nuts, seeds, and dried fruits and vegetables in it).

I need some advice on some high-fat foods for him because he needs to gain FAT weight...on top of that, GOOD weight. As I said, some high-fat and high-calorie foods for my underweight green checked conure