Neighbors, Round-up and Bees

My neighbors have a massive stand of rosemary that, when it’s in bloom, my bees love. My issue with the neighbors–they have no issue at all with my bees–is that their gardeners use Round-up or some other chemical all around the rosemary to kill or prevent “weeds.” When I found out, I explained to them that it’s harmful to the bees and other living things–they have 2 young children who play in the yard–but I have no idea whether they stopped using it. I’m concerned because the bees I started out with went into sharp decline for some unknown reason 5 months after I set up the hive. The queen started laying poorly and they never built up any stores. I am wondering whether this might be the side effect of whatever my neighbors are using. Does anyone know anything about this?