Firstly, sorry to hear about you having a problem after having such a great start! It is unlikely we will get to the bottom of that problem at this stage as the tank was shut down months ago?
What sort of 'cloudy', can you remember? Greenish is usually algae and white/milky is usually bacteria bloom? I have had the white milky cloudiness a couple of times in newly set up tanks and that cleared in a day or 2 without any input from me, but I didn't have anything except snails in the tanks at that time. The PH rising and dropping as mentioned in the other post may have caused havoc with the cycle and if it was bacteria bloom, the bacteria would have drained the water of oxygen so that the fish would be gasping (at a guess)? Did you test the water parameters at that point?
Did anything die with the cloudy water?
Are you planning to have another try? Or has this experience put you off completely?
Simon