I'm not sure your tank ever cycled. Read our articles section and do some googling on sycling a SW
tank. Your fish either died from ammonia poisoning or the stress of living in an ammonia laden tank and got ick or whatever else.
BTW, you've got damsel, not danzels.
The best thing you can do is do some serious reading on setting up a tank, understanding that, and get a liquid test kit to stop relying on the lfs
. After your reading, you'll likely understand just what happened and stop throwing away money. Cycled or unclycled, those 6 fish inside of two weeks was way too many to add to a new tank.
Also, do not ever add any of the water from the lfs
to your tank after acclimation.
Bottom line. You gotta understand more about SW
fish keeping and NEVER rely on an lfs
to steer you right.
Best of luck to you.