That's really sad to hear - I'm sorry.

Did you ever find the other Green shrimp?
I don't know if you want to talk about it at all, but was curious if you used bottled water? Any ideas left of what in the world could possibly be the problem? It's certainly not for lack of trying.
Because of your previous experience, it made me aware I might have some problems too - in my case, very hard water with who knows what metals - and I did. I found some Red Cherries, but bought only 5 just in case. I lost 2 within the first four days, right after molts (or perhaps they molt because they are stressed and dying anyway?).
Since I had nothing to lose, I tried a 20% water change, this time filtering it through the Brita water purifier (using those Brita pitchers) and still used a water conditioner to get rid of chloramines, chlorine,etc. I saw improvement right away; even the Bamboo shrimp seemed happier. Those remaining three RCS molted successfully and are doing fine. It *might be a coincidence that they have survived thus far, but given my particular situation anyway, I'm fairly certain filtering the water helped. Of course it's only been a week but I'm hoping they'll contiunue to thrive.
Point being, wish there was something that could help you; your previous post really did help me and my shrimp.
-GunmetalBlue