big probs

3 weeks into flower from 6 plants i got 4
females got rid of the 2 males ,they (the 4 females) have stopped growing all except 1 the leaves are folding down and they look in pretty poor shape , one of my timers was on the blink its the one that switchs the heater on during dark period and the thermometer has shown that it has dropped as low as 4c overnight this must be going on for a week or so now! ive changed the timer but the plants dont seem to be recovering im feeding every 2nd watering and watering every 3 days ph is fine could the cold overnight have done this much damage? i need some advice dont want to lose them day time temps are holding 28-30c . take a look for yourself the last pic is the only half healthy one left

You HAVE to get your temperatures stabilized. That's much too cold!