One of my Eyelids Droops, Especially when I Am Tired or Towards the End of the Day? (photo)

One of my eyelids droops, especially when I am tired or towards the end of the day. I think it looks better in the morning because it is a little swollen. As you can see, both are normal double eyelids, then later in the day, one becomes a triple eyelid. This is on a daily basis. It is hard to tell from the photos, one eyebrow is slightly lower as well. What causes this and what is the least invasive fix? Botox, other injection or lift treatment? Or would surgery be necessary?