Yellow eye kole tang not eating/breathing heavy.

I agree with Vinny. Take things a little slower and keep things stable. Don't worry about chasing pH. Usually dosing pH buffers also has some alkalinity in it to raise the pH, so you may have dosed a lot more alk than you thought. Stability is the most important thing that I have found.
Keep an eye on your other fish in the tank, and let us know if other fish start showing signs of decline. Sorry about your loss. We've all experienced something like this in the past, unfortunately.

 

Sorry about your loss ..that's exactly what happened to my kole tang though minus the breathing heavy....was fine, then boom, hiding and not looking good - no obvious signs of disease and then he was gone

 

Will do guys, thanks

 

Found the 3rd one. Breathing heavy and unable to do anything but do a short burst to shoot forward a few inches. Stood on its head, side a few times. Here's pictures. Top fin appears to be half missing. Found where the tang normally stayed. This one has been missing for a full day. Do you believe the tang could have attacked him while he was stressed? 2x cleaner shrimp 2x firefish and 6 line wrasse doing great.

 

Fish confuse me sometimes. It has been my experience that coral is much easier to keep than fish. I know that sounds odd but I have always had much worse luck with fish.

 

Me too. I'm going to close the case on the tang got stressed, firefish roamed over there and got killed.

 

There is something wrong....fish just don't start dying off one after the other. I know it was mentioned before, but it still sounds like an O2 problem. Do you have good SURFACE movement? I know you have a skimmer running, but that is not enough. I.E. I had Home Depot putting carpet in my house, and had to move one of my freshwater tanks out of the room they were working in. Within 3 hrs, My Parrot fish was laying on his side gasping. I forgot to put in a circulation pump.Luckily, my son saw him, and I was able to save him. C02 MUST outgas through the surface. When there is no movement, it is like a lid on the top of the water. I would double check. Movement under water does not work. The surface MUST have some ripples going on, either from your returns, or from your circulation pumps. If your params are what you say they are, this is the only thing that makes sense, other than the swing in alk.

 

Return pump nozzles were pointing towards the surface but I've made them more aggressively stir the surface just to be sure.

I may be wrong but I thought the water/bubble agitation of a skimmer helped with gas exchange? This is a drilled tank aswell so the overflow pipe should also be helping out with that as well.

 

Well apparently fire fish don't like being kept in groups in the home aquarium. It's hit or miss to be able to keep multiple according to Google. Hmm..

 

Remember, all of that is happening outside of the main water column. Yes, they do offgas what goes into them, but not what is in their Home, if you will. I am not saying this is your problem, but from my experience, I think it may be worth a shot!