I suggested to the OP a sample analysis which would have long and easily solved this mystery and would tell you everything that is in the sample and also the concentration values. From that list it would be very easy to find the offending source.
You got an addy I can send samples to so you can pay to have them tested for me? I'm barely able to afford meds, let alone postage.
I can easily get samples from each source, should only take a week or so.
Firehound is right on with the systemics... I've used way too much azamax in hydro before and can tell you (from the experience of someone VERY sensitive) that it's completely gone in 60 days.
I think one of the biggest problems seems to be all the products that say "Safe to use up to the day of harvest".... when they're obviously meant for food products that get washed at some point before being eaten.