I'm sorry about your losses!
When you posted the dosages last week I didn't think they were right. The proper dosage is 100mg/kg once and then repeated in 2 weeks. As far as I know at that dosage it will kill all ameobas and flagylites. From what I can recall you were giving in around 300 mg/kg every 2-3 days?
Also, you may want to know that if the overdosage of flagyl doesn't kill them right away it is known to cause tumors/growths which will eventually kill the reptile anyways.
Good Luck.........and personally I would be contacting my lawyer. Since the vet dispenced the medication they are responsible for the animals. If you can prove the vet was at fault then I think you could make a case.