Hi and welcome!! I feel like I'm late for the party :(
Your LFS gave you some majorly bad advice. There is no way a brand new tank can support that many animals. The cloudiness is a bacterial bloom from you adding too many fish too quickly. The tank just cannot support them, and they are being poisoned in their own waste (ammonia, nitrite and nitrate).
My rule of thumb for new tanks is add one fish. Wait three weeks, make sure water parameters stay stable, then add one more fish. Wait three weeks, etc.
You will have to get rid of the tangs anyways, because your tank is just not big enough for any type of tang, so I'd suggest you start looking for a new fish store. Someone will take them in for store credit, or at least a partial refund, even if you didn't buy them there. Or, go online and search for a local reefing club. Many people are generous, and would be willing to "babysit" your animals while your tank cycles, and you should have no problem finding new homes for the tangs.
I also suggest you get rid of the sand sifting star. Sand sifting stars need large, mature, established tanks to survive. It will starve to death in your tank.
I am also not an advocate of sea cucumbers. Reason being, they bury themselves in the sand, and if they die, they release toxins and will just poison your tank. And it'll be impossible to remove the body if it has buried itself.
You should have no more than one or two fish in your tank right now, and a few hermit crabs and snails. The shrimp are extremely sensitive to water parameters and will probably not survive what they are going through. I would suggest getting rid of all fish except the clowns until your tank is done cycling (ammonia and nitrite at zero).
Are you testing the water yourself? I'd suggest doing so, that way you can keep track.
The fluorescent strip light you have now is fine for a fish only tank, but will not support any type of coral, anemone or clam. You ordered the Novas, which are fantastic lights, and you will be able to keep anything you want under those. Those are probably the best lights you could have bought for your tank.
And only run your lights 8 to 12 hours a day. Keeping them on 24/7 is not natural. Is it light all the time in nature? Nope. Fish need to sleep. It's normal for them to change colors as lighting changes. You might notice your clowns getting really pale when the lights go out, or your chromis turning brownish/gray, or your yellow tang getting dark and blotchy. That's normal, and they will come right back to their normal color when the lights come back on.
Good luck, keep us posted, and ask any more questions you have!
