Help with a salt water tank

[mousetap]

I started a salt water fish tank about two months ago. Had the tank up and running for more than 3 weeks. Did a sample water test and the store gave me green light to go ahead with the fish.

I bought two pairs of clown fish and they were doing very well for about two weeks. In between I bought some snails and a flame hawk. After that, I lost one clown fish. Three days later I lost another two. Two days ago I lost the last clown fish and today I lost the flame hawk.

They all had the same symptoms. Usually they stop eating for few days and then isolate themselves from others. Usually swims very close to the top… When I lost two, I took a water sample to the store and ask if there is anything wrong with the water. They couldn’t find any issues.

I really don’t know what I should do now… Any suggestion would be greatly appreciated…