In my limited newbie knowledge, other factors that may explain that sudden death include heat (84 is rather high), aggression (we don't know what goes on when the lights are out and we sleep), or individual variations in fish hardiness (others above have suggested it may be disease-ridden in the first place).
I'm planning to buy Fenner's book too. Good Luck!
7# live rock
2 clowns, a royal gramma, a clown goby, and a banggai cardinal
1 cleaner shrimp
blue, red, green crabs
nassarius, astrea, black turbo, margarita snails