you watered one plant in a 5 gallon pot with 3/4 of a gallon of water??? that is an extreme amount of water for one plant! The point of watering is to keep them moist not to flood them out. MJ is a very sensitive plant when it comes to overwatering. You could flood out the roots and kill the plant!

I have 8 plants all in 5 gallon pots. I give each plant about 1/8th of a gallon of water every 2-3 days.

I think that if the water was just too cold and stunted the plant it wouldn't be so droopy. but they way you describe it makes me think you way over watered! Do you have any pics?