I've been lucky mine are great with the greens and sprouts. I can't get them to eat the roundybush crumble. I give mine very little seed. I would guess its about 15% or less of their diet. If and when I do give them seed, I've rolled the seed onto something that will force them to taste what the seed is on. Like if I cut a grape in half, I'll take the wet part and dip it in a little seed to have them try the greens. If I can get a good way to hide the roundybush, I've tried mash, decorating, all kings of ways for them to eat more of it. If I put seed with the pellets, they just eat the seeds and scream for more food.
My Chaba (caique) will eat everything. I adore him. Not picky but blackberries are his favorite. More than millet! My parrotlets are kind of picky but because of the rest of the flock, they end up trying everything.
I give just veggies and a tiny (I'm talking crumbs here) amount of seed in the morning, if any. Usually mornings are all delicious good organic veggies and roundybush crumbles mixed in. In the afternoon, I refresh with added seeds. I will cut a cooked sweet potato and cut it up in cube or whatever pieces, roll it in seed and serve. They end up eating a lot of sweet potato with the seeds. I do that with bananas, grapes, just about any veggie with any moisture, I will press roundybush and seed into it.
I hope it helps! I'm sure yours will go for the good stuff, greens too! Kale is one of their favorites!