No reboot necessary.
In the AP-Group that those access points are in, go to every Virtual AP and enable "drop broadcast and multicast" (make sure Convert Broadcast ARP requests to unicast is also enabled).
This is not to say that is your main or only issue, but in wireless, since the medium is shared, it could be a number of things that could be your problem and dropping broadcast and multicast in your Virtual AP profile will get some traffic off of that shared medium.
Also, make sure that the transmit power on your access points is between 12 and 18 in that area on both bands.