Hello, My friend has this problem on his clones. I had these exact same clones myself, all rooted without a problem, flowering very well, but he seems to have this problem, and I have no idea what it is, so was wondering can you help? The problem is dem veins turning greyish if you didn't catch it up from the photo.
https://dl.dropboxusercontent.com/u/75717543/IMG_20140408_134617.jpg
https://dl.dropboxusercontent.com/u/75717543/IMG_20140408_134617.jpg