lower fan leaves hanging down

just wondering if nyone can help me with a lil problem, the leaves at the bottom seem to droop and sometimes are a bit shrivelled but the main problem is that my leaves are ok from top to middle then the further down you look the leaves are just droopy, can ny one suggest something to make them perk up? because i was thinking is it the weather, my bubba`s are in a tent (1x1x2) i have 3 computer fan`s a 250 watt mh and i leave the window open when it gets to warm could this be part of the problem? has anyone got ny suggestions as to how i can deal with this issue?

Either you're over watering or most likely slightly underwatering. The lower fan leaves are the first to go when the plant is struggling for something. Or possibly the light penetration is not enough.