Worms or parasites? I was having the same issue with my dogs and at my wits end. All there fecals came out clean. I started to really measure their dog food and not over feed them and that actually worked. I'm not saying its the cure for every dog, but it made a huge difference in my dogs and my sanity.
Misty- Samoyed Mix, Tannor- Golden Retriever CGC
Robyn- GSD CGC, TC, Midnite-GSD CGC,TC, Brennan-Golden Retriever CGC, Batman-Husky/Greyhound , Apollo-GSD