My dog had Giardia and Coccidia when she was a puppy but any vet’s fecal test should find those. Coccidia isn’t always treated as it’s fairly common but my vet treated it as it was only found after three cycles of treatment for Giardia so she felt it best to treat since she was a small puppy.
Considering all you’ve tried and the fact that chicken and rice doesn’t help which is a tried and true solution usually, I would suggest switching out your water. It could be that your tap water has excessive fluoride or other treatments that are disagreeing with your pup. My parents had to switch to bottled water (they just buy the generic at the grocery store in large containers) when their cat wasn’t tolerating a normal diet and had constant urinary issues as well as diarrhea regardless of food.
I also can suggest from personal experience that if you buy high quality no-grain food (you’ve already invested in so much so I don’t think you’d mind. 😉 ) you will typically find your pet’s bowel movements to be smaller and solid as they digest more of the food and don’t have filler waste. I use Wellness Core for both my cat and dog. Each receives a quarter can of wet each day to ensure additional water volume and no constipation. The rest of the day is dry. Wellness Core doesn’t have any grain in it which grains tend to be more prevalent in allergies and inflammation.
Hope some of that helps. 🙂
