Until you have a regular appetite I would try to stick white meat wet foods to add to the kibble. And I would also add a tablespoon of coconut oil. Great for the skin, fur, digestion, nails, teeth, and it helps keep pests and parasites off your pup.
But, they love coconut oil, and it has some great fats that dogs need. And if you really want to make sure they are packing away every meal. Put some bone broth in with their food. Let it soak in for a couple minutes before serving.
They can smell the bone broth and a heightened anticipation of their food I would say helps the overall appetite. And the bone broth soaking into the kibble and wet food just makes everything that much more palatable, similar to what they were eating as they were being weaned off the tit.
Hope this helps!