when did they start drooping? what changed day to day and how did they look before?
it could be over watering or not enough water, how often do you water? thats what counts not really how much water you give but how often....you should wait until the pot is much lighter than before when freshly watered, or stick finger in a few spots i got as far as my finger can go it should be almost dry....you will get a million answers but i believe its about how OFTEN you water that makes them over watered.
Look at how close they all to your tents walls, thats also stressing them pushing them in....i have a tent and if you have any sort of ventilation and negative air pressure, air being sucked in, yuor side walls are probably caved in pushing the plants even more, you cant ever see unless you zip up the tent and go inside...this could be part of the reason.
humidity? how is it, if its not 0-20 you should be alright...
light? what kind? how far away? and tell us about your plants how old, nutes etc....