Wasp problems

The wasps are back , after a season when I haven't seen wasps in any numbers they suddenly built numbers to the extent that they have killed four colonies and cleaned out their stores and brood.
This particular colony was quite strong, it had full frames of brood with bees covering.
It could be that the colony went queenless and the social structure broke down preventing the bees from defending the hive. Or that the entrance was too large too allow the bees to defend the colony
The other colonies seem to be able to cope with the wasps so far, we will be taking honey off next week and will look to improving defenses then.