Hey there, welcome to R2R!! I read your entire build thread. It sounds like you have a grasp of certain things from your freshwater experience which is great but there are differences in keeping a successful saltwater tank that will differ from that experience. My friendly word of advice is that you are moving much too quickly, and a lot of this is apparent from your timeline. You joined R2R a month ago and already put fish and coral in your tank, which using bottled bacteria to jumpstart your cycle isn't unheard of, but certainly for your first saltwater tank and without keeping tight track of your parameters, much too quick.
You don't have to spend a ton of money to be successful in this hobby, that is for sure, but there are certain things you absolutely do not want to skip out on. The most important example of this I found in your thread was your initial cycling of your rock. It is important to do it in saltwater (kept at appropriate temperature 70-78 F) and with a powerhead to keep the water moving in order to let the saltwater bacteria pre-populate your rock and begin to reproduce in order to establish your tanks first natural bio filter. So "soaking" the rock in freshwater would not actually do anything for you in terms of establishing a bacterial colony to process the ammonia after the bottled stuff dies. It is evident by the photos that the tank has not cycled (white rock, white sand, clear water). Fish should NEVER be added to the tank until ammonia is consistently reading 0. Then you know that very initial cycle has completed (the tank will continue cycling for many months to come). Though I saw that you added a couple montipora, I would advise not to add any coral until your tank is at least 6 months old or purple coraline algae begins to grow on your live rock. Keeping any coral will be particularly hard if you are not keeping stable water parameters (either by way of weekly water changes of ~10-15%) or automating dosing and auto-top off and still doing some water changes. Having a highly successful tank without water changes is do-able but unlikely for the average reefer. Bleaching the rock and putting it into the tank without de-chlorinating, rinsing and allowing it to completely dry could have easily contributed to the death of the fish and everything else, but at the very least, it killed off any bacteria that may have been established by bottled bacteria (if it was added before/shortly after bleaching the rock) and probably restarted your cycle.
I think people stopped replying to this thread because things are progressing so quickly and there's so much to unpack in terms of giving you advice and pointing out some crucial missteps that it is just a lot to address. I was not able to get to everything but I wanted to address a couple of what I remembered were important points. Everything may seem like people are over-doing it in this hobby but they're typically not. The show tanks you see are a result of years of research and accumulated knowledge as well as trial and error. But all the research you do up front will save you a lot of wasted time due to error and ESPECIALLY wasted money.
Here are a couple very helpful and important threads to help you become fully informed moving forward (I also suggest reading all the "pinned threads" on this website that relate to keeping a tank). The Bulk Reef Supply (BRS) 52 Weeks of Reefing series on Youtube is also an extremely valuable resource.
https://www.reef2reef.com/threads/the-supreme-guide-to-setting-up-a-saltwater-reef-aquarium.138750/
https://www.reef2reef.com/threads/cycling-an-aquarium.306554/
I say all this in hopes of helping steer you on your way to a successful, stable tank so you can properly enjoy keeping a saltwater tank rather than endlessly trying to correct beginner's errors your entire time owning this tank or worse killing more fish/coral or potentially crashing the tank. Good luck!
