I didn't think that the antibiotics were the cause of the kidney problems, but based on something I read a couple of days ago, I now think
it is possible that the antibiotics were the culprit.
The antibiotic residue that was found were all sulfa drugs. There are some problems when it comes to
some dogs and sulfa drugs (alergic reaction, etc). Sulfa drugs are just one of many classes of antibiotics.
Disclaimer: I haven't seen any scientific sources come out and say that sulfa drugs can cause Fanconi syndrome in dogs (but I haven't really looked for them). So read this link with that in mind, it is an example of what is going around with regards to this issue. I have NOT searched more to see if I can find anything to back up these claims:
Drug Residues Directly Linked to Illness, Death of Dogs Fed Waggin' Train & Milo's Pet Treats | Poisoned Pets | A Consumer Guide to Pet Food SafetyPoisoned Pets | A Consumer Guide to Pet Food Safety