I am having a very similar problem with my GSD Tess, who will be 2 at the end of August. She stopped eating her morning meal but will eat her evening meal, especially if a drizzle coconut oil all over it. I was concerned at first, but them my 1.5 year old Cairn Terrier is doing the exact same thing now. They both just sit there for a minute and then turn and walk away.
It appears to be happening a lot with GSD's who are in tact and around the same age and also heat seems to have an effect on them too!
I was feeding both of my girls TOTW, alternating between the Bison and the roasted Fowl. Then I saw Whole Earth Farms at Petco and decided to give it a try, I thought the ingredients looked good but the price looked even better! They didn't like it, plus it gave Tess the diarrhea, even though I moved them both over slowly. I decided to put them back on TOTW and now they won't touch it.
My husband keeps saying that they'll eat when they're hungry. I've tried adding water to it, canned food, pumpkin, yogurt and even chicken broth. I have to stay with a food that will fit my budget but also be a good food for my dogs. I'm thinking of moving them over to 4health, it's affordable for me and it has a 4 star rating.