Can you give us an idea of exactly what you are feeding your babies every day?I'm going to grind some egg shells up until they can chew on bones. I've decided I don't want to do ground meat. I've been chopping it up & am working toward bigger and bigger pieces until they can handle bone. They have had chicken thigh, liver, heart and quail eggs. I'm going to try and find some chicken heads for the eyes and brains.
You seem to understand now that you need to include a calcium source like eggshell. In case it isn't clear it is *critical* that you include calcium in their diet. This is especially true with kittens. Their bones are growing rapidly and if you don't provide enough calcium you can do them very serious harm.