I would have to agree with Aloner in that a picture would be of better help in determining what could be the issue. However, you said "My problem is the tips of the leaves on the new growth (pistels) are turning upwards and turning white". There's a bit of confusion with your reply. The leaves are not called pistils. The pistils are the little tiny white hairs that emerge from the Calyx which is located where the main stalk meets the fan leaf. Some people also confuse the pistils with the Stipules, but the Stipules are aren't white; they're greenish and thicker than the Pistils. But if you mean the tips of the actual leaf, then it could probably be either light burn from your LED's being too close or from nutrient burn from over-feeding them. Then again, you said 'white'. Most nute burn and/or light burns are usually yellowish/brownish in color and look crispy and curling/drying up in appearance.
I'm currently in mid Veg. and I'm using an LED with less watts than your LED's and I have mine at around 28" above my plant. The plant seems to like it. Early in the morning she raises her leaves a bit, but after a while they're in normal position. I'm just saying that LED's are more intense than some people give them credit for. Which is why it's always good to hang them higher than what the manufacturer suggests. I'd raise those LED's a bit more and watch how she reacts to them throughout the day. If she keeps yellowing/browning, curling up, and/or trying to turn away from the light, then raise them some more. If by the end of the day she's still reaching up for light, then lower it around an inch a day and monitor her. Hope that helps. Good luck with your growth.