Understanding the thermal images of planar pcb coils
Why is only the first turn in the coil hotter compared to other two
  turns?


The inner turn will get hotter because it has less surface area to dissipate heat produced and, it is enclosed by outer turns that themselves will push heat towards that inner turn.


  In this, only the turns of the top part seem to be hotter compared to
  the bottom.


It looks like the 2nd picture has an inner turn that is connected to a central copper circle (I could be wrong about this of course) and that will act as a heat sink for the inner turn at short distances from the central copper.