Yeah, those have to be some tough loses. But as you said at least the little one didnt get shocked or hurt. And you didnt lose any of the other fish. Now he can be taught from this experience that the fishies arent really something we can play around with.
I also find it strange that it was enough to kill the polys. it kind of concerns me because i know my polys have been through similar temperature drops, Maybe not as fast though, and i didnt lose any. Maybe the ones we have just have weaker genetics or maybe theyre just so used to the good conditions that when something did go wrong they werent ready for it.
Anyway, I hope all the fish make a full recovery!