As for poison. There is a sheep pasture and the fence line is sprayed once a year, but nothing else anywhere that I know of. It's some distance before you get to any farm land, although not right in the city. I do not know if maybe a neighbor does something with their lawn. Are there common lawn chemicals that could cause a problem?
>> Yes, absolutely. Here, we have all kinds of insects that like to live in a lawn, so it is common (much more so in the city) to spray insecticides on lawns. The fence line spraying is probably not a problem, that's herbicide most likely.
Another cause of what you describe is a combination of underfeeding and cold weather. My girls have been busy as all get out today, but completely lethargic two days ago when it was below 45 degrees during the day. Last year, I almost lost a hive due to underfeeding in cold weather, but they recovered once I figured out what was going on.
A feeder in the hive is a good thing. The fact that they're not feeding points towards insecticide, I think, assuming all else is OK.