Cool temps + acid soil (you cannot use peat moss without addition of lime) + too wet= dead.

You need to flsuh your plants well with tap water adjusted to correct the pH (2nd link in my siggy), and then let them get rather dry.
Next, re-pot your plants into fresh light potting soil in slightly larger pots with REALLY good drainage -EXTRA HOLES!!!- immediately, and continue to monitor the pH of your nute solution, which isn't really that great for cannabis. I'd recommend switching to a highly-organic one with humic acid, to help stabilize your pH. MY number one choice would be the Pure Blend Pro line, whcih is designed for cannabis and to be forgiving to a wide range of soils and soilless mixes.

You NEED to knwo your room temp, and keep it between ~72-85 day and no lower than 65 night. If you have to add a space heater, well... you have to add a space heater.