Not to step on anybody's toes here, but I think you should figure out what killed your first fish before you add any other ones. From your description, it may have been ick or another parasitic attack. Ick will cause, in its extreme about to die moments, color change in the fish, (bleaching), fin clamping (where the fins are all held close to the body), tattered fins, and death. You should wait at least six weeks before adding any new fish to your tank, just in case it is ick. Also, you really, really should, if you're planning on staying in this hobby, invest in a quarantine tank. Since you've got a microreef, it needn't be a big quarantine, 10
gal would prolly be fine for the fish you can fit in your tank, but unless you plan on buying all new fish every couple weeks, you should look into quarantining all new stock for a minimum six weeks. Many fish diseases and parasites don't become evident for at least two weeks, and it's soo heartbreaking to lose a whole tank full of fish because of one newcomer. I know, I've been there. And remember, a shortened quarantine is almost as bad as no quarantine at all... in aquariums, marine especially, patience is a necessity, not a virtue.
Hope you have better luck in the future.