Thanks for the answers to my questions.
The greenish color which you're seeing simply reflects increased transit time and an irritated intestinal tract and nothing more serious than this.
As you probably already know, there can be a number of different reasons why a dog can develop diarrhea which range from dietary indiscretion to Inflammatory Bowel Disease to viral/bacterial infections to a foreign body...just to name a few examples.
1. However, when I'm presented with a patient who appeared to respond to Metronidazole (an excellent choice for diarrhea issues) but then whose stools become loose again, then I want to rule out internal parasites as the cause even though a fecal has been negative.
Repeated studies have proven that stool samples are not always positive when these parasites are present since eggs are not shed in every sample. So, a positive is a positive but a negative is not necessarily a negative, if that makes sense.
If this were my case, I'd worm with both Metronidazole 250 mg twice a day (a higher dose which should target Giardia) and Panacur (Fenbendazole) which is going to take care of not only giardia but whipworms, hookworms and roundworms as well.
Given that the other dog may also be exposed to the same internal parasites as Bella (even though he may not be symptomatic at this time), I'd worm them both.
2. I would discontinue the pumpkin since the additional fiber may be contributing to the looser stool issues; I tend to use it for constipated patients, not those with diarrhea.
3. I would add a daily, canine formulated probiotic such as Forti Flora which may be available at local pet/grain stores, at your vet's office or can be purchased online (shipped overnight).
4. I'd feed a bland diet of 1 part boiled, skinless, boneless chicken breast and 4 parts 20-minute white rice (organic is fine but it should be white rice, not brown). Feed smaller meals through the day, 3-4 rather than 1-2 and no kibble.
I'm not sure what to make of the hacking that she's doing after drinking water or playing with her brother. I wouldn't consider this to be associated with her looser stool issues unless she ate something which irritated her throat and was something which might cause intestinal irritation.
Most patients with looser stools issues will respond to the above treatment protocol; however, additional testing is occasionally necessary to determine if something else may be going on such as problems with the pancreas or low B12 levels or even IBD.
I hope this helps. Deb