Dear Kelvin.
Fish dying is part and parcel of reefing. Even the experts/experienced suffer casualty. Quite a tall order for beginner/new setup to keep powder series..
To give up now, would mean you will never return to this hobby. However, if you can learn from this unfortunate episode and turn things around, then it'll be an achievement.
In order to help you succeed, why not start by posting your tank thread, parameters, specifications, full equipment, maintenance regime and possibly what livestocks you want in future... Pictures of ur setup would be helpful...
In the mean time, keep your head up! Read and learn more, you will realize that it's really not that difficult.
TGIF!