i know this may be sad to say but when first starting out losing a fish always seemed like it was absolutely horrible, now that it's been the better part of 20 years that i've had fish when i lose a fish it's not so bad, (unless a diskus gets sick and dies) $$$, ok that was a bit harsh, you get use to a slow kill off eventually, as tanks and fish age you will find floaters and sinkers, mostly sinkers, if their floating they've been in there too long and probably have a white cloud around them and can't tell what kind of fish they were in the first place, these things happen, it's life and death and as we get older it just becomes a part of existence and nonexistence, it's when you know you're the cause of said death that's the hardest part, if you know there is something wrong and have a hard time trying to fix it, it makes it more difficult because your fighting for something that you care about, i guess that's why when i go to clean tanks at diff homes and business i notice the diff in caring, homes ppl call me all the time and say ummmm i have a dead fish what do i do with it, (result i say flush it) unless it's too big then i have them freeze it and i take care of it... when i get calls from business ppl they are like how much did that fish cost and can i now put more in the tank? (difference in dolars and SENSE)( hahaha sorry for the banking joke).... zambize never get discouraged this has happened to each of us at some point or another, we have all had a tank that has baffled us to no end and then for no reason at all that's explainable turned itself around and stabilized and bam you have the best tank set up for miles around. not to write a book here, but i can test my tap water at diff times of the month and come up with diff results, regularly, i tend to do my water changes in the middle of the month, reason is that is because the ph is lower in the tap water, due to 1 they treat the main system with huge doses of chloramine on the 1st and the 17th of each month, called and asked, secondly it's when i test the tap water and it's at it's lowest ph, 7.1, i need 6.5 for my discus, you can see where i run into issues with my planted discus tank then. i hope this helps ease your mind a little bit and that after your vacation you come back to a completely healthy, happy aquarium.
Brandon