Dental Chews Problems?

Has anyone's dog experienced illness after being given Kirkland dental chews (Costco's version of Greenies)? I am wondering if I may have gotten a bag that was contaminated.

My 13 year old lab recently had a major bout of diarrhea. I withheld food for 24 hours and then gave him his normal food, but nothing in the way of treats or the dental chews for a couple of days. His stools returned to normal and I gradually began giving him his normal treats (kernels of dog food). I then reintroduced the dental chews (1/day). After about 2 days on the dental chews he again had a bout of raging diarrhea. (This all took place over a period of about 2 weeks.) I again withheld food for a day and then again started him back on his regular dog food. Haven't given him any dental chews since and so far his stools are normal again.

The main reason I suspect the chews is that my daughter was here on vacation for a few days with her English Cocker, and I gave him a chew each day (about 3 days). The next day after they returned home he had an episode of severe diarrhea, heavy salivating, vomiting and was crying in pain. He ended up at the vet's on an IV and seriously dehydrated within a couple of hours of onset. Bloodwork and tests showed nothing abnormal. Because of the rapid onset the vet suspected that he had gotten into some kind of toxin, possibly an organophosphate, but my daughter has scoured the yard, and the house is childproofed because of her 3 year old toddler.

When my Lab had the above described diarrhea it occurred to me that the two incidents might be related. The only thing that they both ate in common was the dental chews. My lab has never been prone to stomach problems, so this was very unusual for him. Even though he did not have the same severe reaction that my daughter's dog had, I surmised that this could have been due to the difference in their comparative weights--The cocker is approximately 25 lbs whereas my Lab is about 100 lbs.

My Lab has been getting 1/day of these for about a year with no problems. What I didn't mention is that this was a newly opened bag of the chews. Is there any way I could get these chews tested?