It could be a number of things. If your plants are getting scorched from the light, the top of the plant would be most affected, but I have to agree with the above poster, 2 times a day is waaaaay too much water. You're probably drowning the shit out of them. I water about once, maybe twice every 7 days. Twice a day is too much. Allow the soil to dry out, then water again. I have learnt so much just from reading this website. Read read and read some more. Include some pictures if you can as diagnosing a plants problems without one, is like a doctor reading with a blind eye.