Some people will add a little diluted chicken broth to hard food to entice their dog to eat it. You dilute it, because it can be very salty.
I think some of the higher quality foods may be more palatable like Natural Balance or Innova and Chicken Soup for the Dog Lover's Soul in hard food. For canned foods, all of these foods are great too. Innova will probably be the most expensive, but with a tiny dog, it really doesn't matter. You don't want to feed your dog a product with too much grain or corn which can cause allergies in dogs and by products are not good either. NB is in the big pet food stores. For the CS and Innova, you would have to search for their site and use the store locator to see who sells it. Innova is naturapet.com and it has a dog food comparison chart, but most of the foods they have listed to compare theirs to are pretty bad, because they are mostly corn or rice. Seeing corn listed first is bad in dog food. Then if you keep reading, foods that list corn in different forms a few times in the same food as well as doing it in other foods with rice are no good, because it means the food is mostly rice or corn. Dogs are carnivores and need most of their protein to come from an animal protein that should be listed first.
Stay away from grocery store brands, and most big pet store brands. Read the label. For instance, Pedigree soft pkgs have sodium nitrate which causes cancer, so you when you switch foods, pick one that is good.
It is okay to switch dog food every 3-4 months so toxics that may be in one food does not build up after feeding the same food over the dog's lifetime. When you switch hard foods, you have to mix the old with the new or the dog may get diarreah, which they may anyway, because even if a food is very good, they all don't agree with every dog's stomach.
Maybe this recent switching of foods is making your dog have stomach problems. I didn't see you say exactly what they were, but plain canned pumpkin (not the pie mix) can fix diarreah and constipation. You just put a tablespoon or so in with their food.
I don't agree with forcing a dog to eat. Sometimes they just don't like the food or decide they don't want to eat it anymore.
Bye, Chilidog