Yeah, we did mention to you that your LFS was way off in telling you to put fisn in an uncycled tank. I'd send all 3 fish back to the LFS personally, and let your tank cycle for a month. Have you bought test kits yet?? If not, you really must buy a kit and a refractometer to check your salinity.
Seriously...we only want to give you a good start to your aquarium, so please listen to our advice instead of the LFS -- return the fish, cycle the tank with just fish food or table shrimp, check your ammonia, nitrites, and nitrates -- and salinity, before you add any more fish.
Out of curiosity, which LFS did you go to? I know of 2 reputable ones. Hopefully you did not go to Wally's Aquarium or Super Petz (ironically both are in Annandale) :shock: