Sorry to hear about your Elegance, I can relate. I've had an Elegance for 2 months now. I kept one of the old hardy ones for 5 years 10 years ago that grew into a monster. The one I have now is a lime green and was a Premium Aquatics Cherry Pick. They told me they also had bad luck with them for a while but they found a new supplier that they have been able to get healthy ones from.
Like my other Euphyllids, I feed it small pieces of chopped krill 2 or 3 times a week. I also have 4 Goniopora in the same tank. Two are doing well and two aren't. I add some DT's Phytoplankton, Liquid Life Marine Plankton and some DT's Frozen Oyster Eggs 2 or 3 times a week for the Goniopora. This tank is run as a "Lagoon" type tank, light skimming w/refugium and the only fish is a lone Purple Firefish. Any other fish (Flame Angel, Copperband Butterfly and a Mandarin Dragonet)I have put in this tank die unexpectedly within a week, so I quit buying fish for this tank.
In my 75 I've tried Acropora several times, but I think the other corals in the tank are producing too many toxins for any new corals to have time to adapt to the allelopathic compounds present in the water. The first Acropora ( a large $175 purple branching one) I tried in the tank lasted 3 months and then slowly RTNed in a week. I've tried 2 more small Acro frags since then and neither one even made it through a night, so I've given up on them. I have a good skimmer (Aqua-C EV-180 with an Iwasaki 30RLT) and a refugium on the tank and everything else is thriving in there.
Anyway, you will always have some good and bad luck/experiences in this hobby and unfortunately the bad ones are usually expensive. IMHO one of the best investments you can make is to purchase Eric Borneman's book "Aquarium Corals" as a reference to assist you in any future purchases. Bottom line is you never can predict if an organism will adapt to the conditions in your tank or not and there is always the chance that it won't. Even if your water parameters are good, there are many allelopathic compounds that your corals put in the water that we can't test for. Basically every tank is a "Chemical Soup" of unknown and toxic composition.