A healthy looking plant like that droops more from heat but it's just a guess. What is the temperature at the top of the canopy?

The Shultz Cactus nutrients is closer then the flower stuff fyi. Still not the best but it is easy to find. You should be using full strength nutrients at this stage the plant is large enough to take the extra nutrients but watch for over feeding then. You are only using CFL so the plant will not grow as fast. So even cutting back the nutrients from full strength to 3/4 strength may be a better idea.