Seems like a lot of experience on self treatments and diagnosis here however, no mention of one critically important factor. Temperature. Dogs get the *censored*s. They eat stuff, drink stuff and we get to be the recipients of their liquid blessings.
If a dog has a bad case of the *censored*s, taking their Temperature is one of the first signs of what is to come. If their temperature is elevated, its a good time to see the vet and get the source of the issue figured out. If, temperature is normal, proceed with whatever home remedies you think work best for your dog. This still may not be the best answer but, most commonly dogs will start running a temperature if something real bad is going on. They can also drop if something worse is going on.
Your diagnostic tool is a $5 digital probe from any grocery store jammed in their butt til it beeps.