Nutro is not a very good food, if you Google "Nutro Consumer Affairs" you will see a lot of issues. Dogs even died from it before. I don't know if they ever fixed the problem.
But anyways... my dog is VERY picky, too... the only food he's consistently eaten and loved is Nature's Variety Instinct. He also just started on Fromm Surf and Turf dog food and loves it. These foods are not available at the Petsmart, you have to find a mom-and-pop type pet supply store that sells them. If you find the official website of the food, you type in your zip, and it gives you closest stores available!
Good luck!
Jackson also suffered from kennel cough and with some antibiotics from the vet, it was gone in a few days. He was making a terrible coughing/hacking/gagging noise mostly at night and in the morning.