First dead fish since October of last year :(

[mrhasan]

So my banggai cardinal died which have been living in my tank since last October ; the month when I finished adding fishes to my tank. With no apparent reason that I am aware of, she died today The only fish that died few weeks ago was my firefish which jumped out unnoticed while I was adding some more live rock to the tank.

Other fishes and corals are all looking normal. Fishes eating and no sign of stress. Corals have their polyps extended too. I checked for ammonia, nitrite and nitrate and things are all in check.

I was just wondering whether I should be worried about something or it was just a misfortune.