Compressed Crumb Structure At Edges

Could someone explain if this would be a classic case of underproofing?  Baked 2 rye loaves this weekend.  One turned out bit dense and sour and the other nice flavour and more even crumb.

Photo 1 has less open, and dense compressed crumb at the edges near the crust.  This one was proofed room temp for 1 hour:

This one has a more even crumb throughout and less sour.  Proofed for 2 hours.

My main question is if the only factor for the compressed crust edge crumb would be underproofing and not anything else.

Anyone who would have a reason why the loaf that was proofed for an hour was much more sour than the one proofed at 2 hours i'd appreciate an answer on that one too.  Both loaves came from the same dough.

John