Well this is varroa-free country and I have double checked for mites... so that is not the case.The smaller bee is a victim of varroa mites feeding on it's blood. It is underdeveloped, has deformed-wing-virus and will die shortly are emerging. The larger bee is fully developed and probably died of old age. Check your hive for varroa infestation levels and take action as needed.
I have had the bees from 2011 and the colony in question has a very vigorous queen. The queens are supplied from the Aaland Islands archipelago which are varroa free.I suppose it's possible this bee could have been exposed/infected with some of the viruses that are normally vectored by varroa mites. Is it possible your bees were supplied to you from some other country that is not varroa free? How long have you had these bees? A better picture of the small bee would be helpful.