This link backs up what is in the link above (although the info is in relation to humans, not dogs):
http://www.ccjm.org/content/69/4/289.full.pdf
The third page of the link above has a table that shows that sulfa drugs can cause "Acute Interstitial Nephritis," and Fanconi syndrome is associated with AIN:
Medscape: Medscape Access
We may indeed have the culprit. I sure hope so, because that would mean this could be tested for and prevented in the future. However, even with testing I have NO faith in any food products from China, so I won't buy them anyway.