I wish I could help you, but haven't a clue as to what is going on. I did a bunch of Gray tads this summer, but didn't have any issues.

Would it be possible to get one of your tads or froglets necropsied? Is there a vet with that kind of specialized knowledge that you could consult? Could you possibly have some sort of parasitic infection going on?

This must be extremely frustrating for you.