Identify Cause of Death [Pictures] Tiger Barb

[Morgoth]

Hello,

I have recently had a loss in my tank, and I believe I know what caused the fatality. I am, however, still quite new to the freshwater aquarium hobby and haven't seen everything yet, but I have seen a bit.

Since I want to test my own knowledge as well as the knowledge of the members of this forum, which I am a new too, I will hold off from giving out my tank information until I get a few replies and can post my opinion.

Here are two pictures of my Female ~1.5yr-old Tiger Barb postmortem. If you'd like to give it a guess please let me know what you think.