The gorgonian and the goniopora have poor success rates in closed systems. The gorgonian is not photosynthetic and relys solely on food from the water column. That said, I doubt it died that fast without eating.
Don't get discouraged. I killed a lot of corals in the beginning. I still kill corals from time to time. Everyone does. Anyone that says they don't lies.
Meanwhile, research things before you buy them. Any gorgonians(also called sea whips) that have white polyps are non photosynthetic filter feeders. They need a steady supply of food in the water column. This is a difficult task in a closed system. It's hard to keep good parameters when constantly adding food.
What are your current parameters?