Why are my tulips drooping?

Are they not getting enough water? I watered them today but it seems as though a few more have taken a turn south. If it's just that they need more water I apologize for asking such a simple question--I just want to make sure it isn't something else they might be lacking.

Thanks!

What kind of tulips are they? Are they in full sun? When you say drooping, do they look top-heavy because of the weight of the flowers or foilage, or wilting? My guess would be that they may not be getting enough sun or fertilized with too much nitrogen.