I want to thank everyone for your responses to my dilemma. I have, as
expected ,  learned a lot from your input. I am grateful, that I've lost only
one hive in the 7 years I've been keeping bees. Of course I only had two
hives for 5 of those 7 years. I guess this year my time came to pay my dues.

   I am inclined to leaning toward my problem being a ventilation problem, as
I believe the bees had plenty of honey stores. We live and learn.
  Again , I appreciate everyone's help.
Best regards,
Denise