Although little watering can cause this, I believe the drooping is from the lights being turned off.
Someone posted this response on youtube which answers the question
"its cuz of the light cycles. when u flower a plant its 12hrs light, 12 hrs dark, notice how u dont see any darkness cuz its all shot under light. so at the start of the day the leaves are lower because they didnt need to stretch out towards the light. just like all plants grow, they grow towards light, and ease up when its dark " (city4eva204)