Hmmm. I have 4 week olds, and I've fed them dried and live mealworms (will cut the live ones in half next time. I think they had a bit of a hard time with them), dried and fresh veggies (in small bits), dried alfalfa, fresh grass clumps from outside, some dandelion weeds, and every night I plug in my bug zapper, and set it on a paper plate. In the morning, I have about 2 cups of mostly dead, but some live, BBQ bugs. My chicks go crazy over them, and then spend the rest of the day scratching in the wood chips looking for the live bugs that escaped the initial massacre.
I have a cup of chick grit that they can free choice from. They also have free access to their chick crumbles all day.
Have you tried just scattering whatever treats your feeding in the cage, rather than in a feeding dish? Mine hit the ground running the second they hear the first one hit the ground.
Just keep trying, eventually their instinct will kick in. Do you have pics of your little ones? I love seeing the baby pictures!