What are these droops in the drywall?
Its hard to view the pictures on my phone, but two possibilities I can see:

The ceiling drywall may be unsupported at the edge.  Usually you put the ceiling up first, so the wall drywall supports the edges of it.  You can't do this (easily) if at some point only the ceiling was repaired.  This could make it flex down a bit between the joists it is screwed to.

Poor taping and mudding.  Between sheets of drywall you use tape (basically strips of paper) and mud to smooth out the edges.  Some of those look like the tape started to pull away from the ceiling before the mud hardened.  

If it hasn't changed, its nothing to worry about - just a cosmetic annoyance.

Edit:  Looking closer from a computer, I'm almost certain that's just a poor taping job.  You can clearly see the inch or so line across the seam where the tape is.