Thank you for the reply. I do not know the name of the weedkiller used. the owner of the 5 plex next to me is not on site.
There were some dead bees on the ground, however the majority were dead inside the hive, not in the feeder or on the frames but laying on the bottom board. I have been waiting for a dry day to take the hive apart.
After Dewy's presentation on Tuesday, I thought the hive may also have starved as his slides looked very much what I saw on the bottom board. I had just replenished the feeder with fresh syrup 2 days before, so tey had foos available.