This is my second time growing autos. I'm using super skunk from sensi seeds. Everything has been going well but today ( exactly 7 weeks in ) I have noticed that leaves are starting to turn yellow and drying out/falling off and also the plants aren't taking in the water as fast as they use to, I'm using a hrydro tank system with 3 X 600w lights on a 22hour on 2 hour off cycle. The ph is sitting around 6.2 and temp of room around 19degrees. Does anyone have any idea why my plants are slowly drying? Thank you