First Grow - 4 Weeks into Flowering (Curling Leaves)

First off, I did check the Problems and Cure thread along with a number of other threads/websites, but nothing seemed to give me a definite answer.



Our plants are about 4 weeks into flowering and look pretty good except that the leaves towards the top are starting to curl down. At first we considered a watering problem, but after multiple moisture readings it seems that the plants are getting enough water. I read that it could be due to a pH imbalance. When I checked the soil pH today it was at 7.0 (a little high, but still neutral).

Any ideas what could be causing this? Any solutions to this problem? All/any advice is appreciated, thanks!

Sorry for the low quality cell phone pics.

USING:

400W HPS
12/12 Cycle
Fox Farms Ocean Forest + Light Warrior Mixture
Fox Farms Nutes @ 1/2 Strength following Feeding Guide

I got the same problem like you. Apparently it's stress, heat stress perhaps.

Looks like heat stress man. What are your temps and how close is your light? With a 400 watt HPS I wouldn't be surprised at all if that's what it is. It may be a p deficiency but I'm not positive. What is that planted in? What kind of system are you running?

That could definitely be the problem, we're growing in a tight space (closet) and this 1 plant is a lot taller than the others and shows the worst signs. I should've thought about the light distance.....