It seems my baby Tanis doesn't really like live feeders... he seems to eat only one or two, but he'll ravage a mint plant from my backyard when I bring it in clipped to the inside of his tank. I'm worried about him not eating his insects, but at least he's getting good plant-matter. Also, I dust the plants with Rep-Cal for him so that should help a bit .
How old is he? If he is still a juvenile/sub adult I would take his greens away for a little while or just not offer as much. Eating greens is a great thing but If he is still young he needs to eat all the protein he can get his mouth on.