Hi Chris, I've just found this on Planet Catfish about Gold Nuggets,
L081 is reported in DATZ to represent three very similar small spotted gold nugget plecos. Reportedly, the first is very hard to keep alive for any length of time; the others are considerably more hardy. While these fish may represent the range of population, it appears that the browner (as opposed to black) and finer the spots (amongst comparatively sized specimens) the more likely you are to have a hardy type. Little is know of what this fish looks like at adult size.
So the one that sadly died may of been the less hardy type. Best of luck with the other one. My LFS has just had some delivered but will be a week or 2 before they go on sale, I'm torn between them or a coulpe of L 333, they look great also.