well glofish are zebra danio's. which are hardy fish.
I'd suggest checking the parameters of the water, like pH and all those.
However If only one died I can't say it was the water conditions that did it. It could have had other factors.
Was the tank cycled with or with out the fish?
Read over this topic, it might explain more on the cycling of the tank
I've never bought glo-fish, however I plan on adding them to my danio/tetra/killifish tank in the future.
Because of this I can't say they turn clear upon death. However other fish do turn slightly transparent upon death.