Hey, don't beat yourself up, no one here is going to because you bought your bird! That's reserved for those other forums where everyones perfect.
You can hang kale or romaine lettuce in their cage, rinse it with water and leave it wet, they like that. I also use a potato peeler and slice thin slices of sweet potato and carrots and hang that in their cage too. They seem to go for leafy or thin stuff rather than cut up. That's with my budgies, others may have different experience.
You should offer them pellets, I put them in a seperate dish and hang it near the perch they use the most. Some people mix the pellets with the seed but my guys will not touch it that way. A good food to mix with their seed is Higgins fruit and veggie mix for small hookbills, they seem to like that.