I've been having a similar problem with my 5 month old. We've tested for all bacteria, EPI, and a couple other things. I had him on Natural Balance Sweet Potato and Bison. It improved from the Solid Gold Large Breed puppy so I was thinking he just was allergic to something in his food. The Natures Balance is a limited ingrediant and grain free but his poop was always a little off here and there. I do give him yogurt, pumpkin and blueberries here and there. It still didnt matter what I gave him, it was still "soft serve icecream" style like yours lol. I take him to a puppy socialization class every Saturday morning and there is another GSD that is 6 months old that had a similar problem. She switched him to raw food and has never looked back. I had started giving Brody raw food a while ago but the doctor made me stop in case he was having a bacterial infection from that. So the last 2 days I have been giving him Bravo raw food for breakfast and lunch and then for dinner I just give him the kibble with some cottage cheese...his poops have never been better, they dont smell like they used to, and its alot less poo! So I'm starting to do more research on the raw food, and eventually I'm going to go to all raw food. I got some books ordered that I can read. I know people say it is really simple, but I want to make sure I have a better understanding of how to do it. The Bravo food is more expensive, but its helping him so I'll stick with it, and eventually I can do my own raw food from the grocery store! Just a suggestion but maybe either try raw or a limited ingrediant food like Natural Balance. Don't try the venison flavor, that gave Brody the runs too!