Droopy leaves usually means either over- or underwatering... and given their age and height, I don't think you're giving them enough water! By this stage, for me, in a 3 gallon pot, I'm usually giving them between 1/4 to 1/2 gallon of water every day. The heat is also having an effect on them - very hot!! Which will make them drink more. When you water, make sure you are watering thoroughly - water enough so you have about 20% runoff and then wait until the soil is completely dry to give them more.
You're also going to want to reduce the humidity now that they are in flower... with the combination of high heat and humidity, you're going to run the risk of bud rot which you do NOT want!
Good luck!