Why are my fish dying?

You have to give the tank time to cycle.I find its best to cycle new tanks with goldfish. The goldfish are cheap and easy to replace. you should also use water conditions like start right with allantoin from the makers of jungle fish care products. You can puts some of your rocks from the goldfish tank into the new tank since the rocks contain the good bacteria for the tank. This should help the tank cycle faster then after the cloudy water clears then you a free and clear to try the mollies. make sure you keep the water temp between 68 and 78. for best results try aiming for 72 - 75 degree water. you should also have some type of algae eater to keep the tank clean. weekly water changes of 25 - 50 % of the tank will also help the tank to cycle. Hope this helps you..