I have a Lutino cockatiel that is 30 1/2 years old! Yes, that is a picture of him. I have had him since he was about 3 months old. Good for you getting Fred off a seed diet. I think birds are a lot like children; sometimes they won't eat certain vegetables because they aren't the texture they like or maybe they prefer them raw over cooked. Try chopping or grating a raw vegetable and offering it to your bird. My cockatiel used to like cooked butternut squash, mashed. He likes broccoli now, but he likes it best if I chop it up in small pieces. He also likes grated raw carrots. When he was young, he loved frozen mixed veggies, cooked. I think he might have liked the different colors. Some owners like their birds near them while they eat. It can encourage the bird to eat if the bird sees you eating. Or if you have other birds, sometimes your bird will see them eating a vegetable and figure out it might be something good to eat. That's what happened to my English budgie; he saw the lovebirds eat kale, and then he decided to try it. Don't give up trying to give them various veggies. My cockatiel loves Avicakes and Nutriberries. Sometimes I put the Roudybush crumbles or pellets in his food, but I don't think he eats it. You could try making a foraging toy and putting some pellets in it. Maybe the cockatiel might try eating them that way. Also, if the cockatiel gets plenty of exercise, that might stimulate his appetite to try more of a variety of foods.