I agree with big red. After talking to you on other forums, it seems like you didn't take the advice. Your tank wasn't cycled properly. This can cause issues.
Also, when you take the rock out of water, there is die off, that could have caused ammonia to kill the fish. Now probably not that much though.
Have you tested your phosphates?
I'd like to see all your parameters in pictures of the tests.
The clown may have died because you moved him around so much so he was stressed. Salt is a little low, but nothing to cause an issue.