This could be one of a few things.
A) You have over watered your plant, causing it to droop. The root-zone does not have enough oxygen. I see that you're growing in soil, when doing so it is important to add soil amendments such as perlite or vermiculite, to increase drainage and promote oxygen around your roots, which is important for proper nutrient uptake.
B) You have over fertilized your plant. I'm not sure if this is the case, it looks a little strange for over-feeding.
C) Often times if the PH of your soil is too low the plant will begin to wilt and show drastic signs of deterioration. Certain vital nutrients are unavailable to the plant if the PH is too low, or too high. I would check the PH of your soil and try to balance it to around 6.5 to 7
Good luck.