Ok, well firstly, your LFS advice is nonsense! All tanks go through a cycle, unless you get special additives to help stop the tank cycle. I can almost guarantee that your tank is currently going through a cycle. It's a natural process. It happens in pretty much any tank. So that could be why you've lost some fish already. The fact that the water has been "cultivating" means nothing. It's all about the Live Rock. The live rock will have a little die off, which causes your ammonia and nitrites to spike. These are the 2 things that will cause poisoning your fish and could be lethal.
Now secondly, buying 2 blue Devils was also a really bad idea. They are extremely aggressive and the one probably killed the other one. Also, make sure that the "Royal Grammar" is in fact a Royal Grammar and not a Bicolour Dottyback. They are also extremely territorial and could kill some of your other fish. The Clowns could be in danger from the Devil and the Dottyback (if it is indeed a dottyback).
Also, that is way too much livestock to add to a tank that small. You are going to have some serious problems trying to keep the nutrients in check with so much livestock in such a small tank. The LFS in question should have advised you of this. This is the single reason that I only deal with the Sponsor LFS's that are on this forum. Their advice is always sound and they want the best for your livestock, not the best from your wallet...
If I was you, I'd take all your livestock out of the tank and return it to the LFS, or ask a friendly reefer in your area if they could stick your Livestock into one of their own quarantine tanks until your cycle has completed. Do it for the sake of your livestock.
But, we are all here to help you. Please don't take this too hard and just listen to what all the members advise you to do. We are all trying to help, not knock you down! It's poor advice from a pet store and not a true reflection on you. The name of this game is Patience, research and then some more patience after that.
Good luck dude...