As a marine reef keeper
(voted best home reef tank in the NE for 6 months in a row by Manhattanreefs.com),
I assure you it has nothing to do with that sunlight-
and everything to do with the lack of proper maintenance.
With marine tanks, there is always a lengthy biological break in period,
and the first fish put into a new system are always at risk of dying-
they just put too much in too fast, and didn't properly keep up with it.
130 gal home reef