I don't see how tap water would make a difference, its been 3 months. The temperature, could be a possible problem but at that stage unless pH is around 5 or 10 I don't see how it could kill fish, I've tested worse and the fish are living fine. Look, a very risky thing to do is skimp out on live rock, in a reef aquarium it is going to hold a hell of a lot of benifical bacteria in your fish tank. I would suggest, stop wasting money on fish, and buy some live rock, start the cycle again. Your tank sounds like it is almost certainly crashed. What type of filter are you running, if it is a canister allow it to cycle for longer, then, introduce fish at a rate of 2 fish per 3 weeks. Until suggested stocking levels have been reached. If you have a sump, I don't understand how it could've crashed if it was bigger then your display tank which leads me to believe it cant be a sump. if yourfilter is a hang on or internal don't bother it won't be able to support the desired number of fish you are looking at. Anemones do take time to die, its not an over night process like fish. the signs your fish are showing are all aligned in my opinion with extremely high levels of ammonia and nitrite. Do your self a favour and stop buying fish, get yourself pH, ammonia, nitrite, nitrate test kits. Buy a hydrometer. Get a heater if you don't have one, and a thermometer. Tell us all the readings. Buy live rock, start the cycle again. This way you will save, money, you won't be as frustrated and you will start enjoying the hobby because you will learn to understand the tank. Did you change the water in your tank after the fish died? If you didn't you haven't removed any nitrate. Extremely high level sof nitrate can cause fish to die over a period of time, however not in tthree days which is why I doubt your tank is cycled. I hope the advice helps, I am not bashing you sorry if I come across that way. Goodluck with the tank and we are all waiting to help you out.