I think you may have several problems going on.....the curling leaves and edges could be due to overnute/overwater/ph issues. You'll either have to correct all three or correct them one by one and see what straightens out and what doesnt.

Really NOT a very good idea just to add a ph adjustster indiscriminately (sp?) unless you ARE checking your ph and making sure you are adjusting it to the correct level....between 6.2-6.8 for both your soil and your water. Id slow your nutes WAY down and not water unless the plant soil appears dry.
Weedhound Reviewed by Weedhound on . minor leaf curling and drooping problem hi all, my plant is a double dutch strain and is nearing the end of vegetative growth but i have now noticed that many of the leaves are curling and/or drooping. i have included pictures. i don't know if this is a fairly minor problem or not. i have had it on a 18 hours on 6 hours off cycle under one 240 watt HID lamp and have been using 15ml of plant grow mixed with every 10 litres of water. i have watered it once a day and allowed it to drain through. the temperature day has been Rating: 5