If droopy for extended periods of time, it can be a sign of trying to give it too much light per day. If this is the case, other symptoms will show up and make diagnosis less of a guess. shorter internodes, interveinal damage, stunting of growth etc etc..
I've had it where it took several weeks before they started to get droopy and another week or two before it showed some more signs of light stress. If only off by a little bit, it can take 'forever' to see the results of the error. People tend to focus on the most recent behaviour, but when things are nearly right, it's weeks if not months of cumulative effect that leads to what you see today.