leaves getting burned

hey guys,

leafs on the plant are getting burned, been in growing stage for about 3months? and all of a sudden the leafs are falling over at a slight touch and they fall off. but the rest of the leafs still look healthy.

ph is at 5.5 and the neuts are correct. it gets watered every 2-3 days, under 1 450watt, is it getting the life sucked out of it because its not watered enough?


thanks alot.

edit: its in coco fiber