Wouldn't worry about the leaf, on my last grow I had a leaf that was almost completely white on one hand. Never seemed to indicate any problem or hurt the plant.
As for the drooping, my guess is toxicity. Leaves are looking pretty dark, probably early nitrogen toxicity. Ease up on the nutes for the next couple feeds. Ec meters help a lot in this case.
If you're on a light schedule, leaves might droop right before lights out. If they perk back up in the morning, don't worry about it.