Just comes down to the excitement factor with a tank that wasn't ready. Take some water to the lfs and have it tested. Wait 2-4 weeks before adding any fish. Add some snails and crabs if you need it for algae control.(if its out of hand its a sign of issues)

 

You need to clean out the mag once a week. The poop and other unwanteds are fermenting in there and can/do cause issues with water quality. Your sump/fuge will do wonders for your tank.

 

Also do what you can to cool the tank off. I run mine at 73-76 at all times. I worry if it gets to 80 and would be having fits at 82. I know many run their tanks at that temp and higher with out any issues but it worries me. (higher temps= higher metabolism, more poop etc.)

 

Again its just my opinion.

8-14 dkh/

140- 250 ppm

2.8-5.0 meq/l

What supplements have you been adding? Stop adding all supplements and let the Alkalinity settle down on it's own. It may take a couple weeks. Also check the Calcium which should fall between the range of 350-450 ppm. Let us know so we can help you know how to keep the levels where they should be.

 

As Dion said many of those were risky fish to have in a tank that young.

As a reef aquarium matures it stabilizes and becomes a healthier environent. In a new tank that is set up properly, it's not the Nitrogen compounds that are a problem and usually not the Alkalinity, the Calcium or even the pH. Tank health improves with age reaching optimum after a year. It's hard to describe but a lot of the tips and clues to this are found in the thread below. I recommend reading the entire thread and the extra links as well. There is a link to some good information regarding Ich that you will be glad you know before adding the next fish. Which, btw can be added immediately but don't overdo it.

You have come to the right place for making this tank enjoyable.

 

 

A comment regarding Temperature. I have found it best to set the heater to come on at 75. The tank does very well at 75 and then there is less risk of it going over 80 by the end of the day. I try to keep my tanks from going over 80 because that seems to be the point at which many coral start to show stress. When the temperature is over 80 in a reef tank without robust circulation, fish are okay but coral get bothered.

Hope this helps.

Disease/ toxins? Anything around the tank? Do you use fresh activated carbon?

Not familar with that ppm reading for alk. Did you get the meg/l reading? I doubt that's the issue for you though. Sorry, I'm out of ideas

What were the actual results? 

My guess would be you have/had a low Ph with that bio load and need for more flow. You need good oxygen exchange. The fish may have suffocated. Do you by chance have a glass top on the tank?