Fish Dead

On calling home today I find out my fish had died. Had sad feelings all day about it. If I had stayed home in Canada they would no doubt still be alive. I tried my best to keep them strong and healthy while I was away. changed the filter, automatic fish feeders etc. but less than 2 months after I left Canada they are dead. I had a huge iridescent shark in the tank that was at least 15 years old, FUCK, feel terrible that I let him down. That was one tough fish, now gone forever, will miss watching him when I am back home.