from the pic you have there doesnt seem to be a major issue, i leave my fan on 24/7 and my girls look fine, but my fan isnt blowing directly on them, theres at least a foot or 2 between the plants and the fan and by the time the air from the fan gets to the back plant, the air isnt blowing very hard, could be the way it wants to grow, temp., maybe ph but there doesnt seem to be a nute deficency, trying leaving the fan off at night for a couple days see if there is any change.