Jen,
You may find it isn't the food at fault. When the dogs are out they lick the ground, often the areas where other animals, dogs and cats have urinated. It's possible they've picked up an intestinal infection. There are so many possible causes for illness and really, you need to take them to a registered vetinary surgeon as recommended by the VetinAsia guy/girl. FYI, The Ark in Third St, Sai Yin Pun, is open 24 hrs...but for 'peace-time' normal hours, just ensure wherever you go the vet is registered...ask them at the clinic's reception. Deworming is necessary in HK. So is Heartworm treatment...and 'Tick Fever' prevention. Let's put it this way...they NEED to be seen and checked at least annually. A blood test may be required for analysis.
One school of thought is..when a pet is ill...and not obviously life-threatening (i.e. bleeding, breathing difficulties, accident etc.) then wait a day then see the vet. However, my practice is to see the vet immediately unless I'm fairly certain that it is unnecessary. I've had years of experinece in this, although not professionally medically trained.
Good luck and best of health to your pal,
Sarawesi