I'm sorry to hear they won't eat the prescription food. This is a common problem and most vets aren't too sympathetic about it but it's hard to see your babies hungry and not eating.
My moms dog was recently put on KD for kidney problems and of course he hated the wet and dry food and won't eat. Mom did some research on the web and found lots of recipes to make at home. She now cooks the proper foods for his condition, freezes or refrigerates a bunch and then feeds him his meals. It is a thought and maybe worth a try. Lots of the recipes call for chicken and other meats mixed with just the right veggies that supply the right supplements for their conditions.
I hope this is of some help and maybe you can find something that he will like.

Good Luck and prayers coming your way.