Fishes dying dont know why help pls

It does sound like you care about your tank, but from the video and most obviously the test results, particularly the ammonia and nitrite, you are only setting yourself up for failure. A healthy reef tank should have 0 ammonia and 0 nitrite, end of story. If you are showing ammonia, it means one of two things, that you never really cycled your tank, or that you are overstocked and the bacteria can't keep up what the bioload in your tank. Seeing your tank, it's no surprise that the butterflies did. They are not very hardy fish to begin with, that added with the ammonia explains their deaths quite well. The red you saw around their heads/gills could easily be ammonia burns. I find it very irresponsible of you as a hobbyist to have that many, and those types of fish in that size tank. I don't want to sound "mean" but I take this hobby very seriously. To me, it looks like you had no livestock plan and just added fish that you though were cool or that you wanted when you went to the lfs. I highly suggest you come up with an actual live stock plan, look at eat fish's space, food, territory requirements and decide what you want to keep and what can go. I highly suggest removing the tangs, the yellow will probably be fine, but the hippo and sailfin both get very large, very quickly. If you don't do anything, I see you losing more fish as they grow, compete for space and territory. Hopefully you take this advice and the other advice people give you seriously.

 

Water is not "perfectly clean" with ammonia and nitrite readings.

You said your fish are dying and said you don't know why and asked for help. Heck that's the title of the post! Then you proceeded to discount every reason given saying it's this or that and not what people are telling you, then saying nothing's dying? If you know what it is, there's no need to ask.

You're overstocked (self-admittedly) and this is causing ammonia and nitrite (you admitted you have non-zero readings), which kills livestock. Nothing more to be said, really.

 

Any update?