Hi, this sounds familiar to me
My CSW started with NutraGold and had diarrhea most of the time, she even had to be at the vet some days. Then we changed to Purina ProPlan... it went better but sometimes diarrhea was back and she was very skinny. Then we changed again to Satisfaction and it's the food we are giving until now. She is strong and energic, likes the food, makes less poop and all the intestinal problems never came back again.
Don't know if that's a breed problem but... her siblings had similar problems.