I dont know much about how to solve things since I am still a noobie at this, but posting up information about your tank would help others who are more knowledgeable.
How big is your tank? amount of live rock? dry rock? sand? filtration? what kinds of fish? how have you been adding salt, mixed or just adding it to the tank? powerheads?
I can tell you right now adding any fish to a SW
tank in 24 hours isnt good unless your moving from an old SW
tank to a new one.
Your ammonia, nitrite, and nitrate are all high right now due to the tank cycling.
Here is a great article about it:
Cycle your salt tank
If you did get expensive fishes, I would try to return to get store credit so that you can re add them later. Tell them that the advice they gave you is clearly wrong and that if they believe that they can add fish to a brand new tank, I would like to see them try it for themselves. Adding fishes to a SW
tank that hasn't completely been cycled is very disastrous due the the fishes being extremely sensitive to changes in ammonia, nitrite, etc. Some people can be lucky and add fish early in a FW
tank, but that is still ill-advised since putting any fish in dangerous water is wrong.