Help with new fish death

[AustinW78]

I have a 40 gallon reef aquarium that I have had set up for around 3 months now. I have two baby clown fish two Cardinal fish and one clown goby in there currently. All of my water testing, tank cycling, temperature, and salinity have all been checked and are good. I had a royal gramma that I put in there around a month ago that was doing fine. Last week I added a Midas blenny, 2 Days Later the royal gramma died. Today 2 days after the death of the Gramma the Blenny has died!! I am at a loss for why this has happened. If anyone can give any insight as well as possible other fish that are not going to be a waste of money I would greatly appreciate it.

 

[KrisReef]

You might want to post a white lighted image of the remaining fishes for folks to examine the skin of the survivors.

Often times, additions into small tanks continue until over crowding (the fish decide if there are too many) causes aggression and often death(s) from injuries and disease will follow.