Perform a stress test of the network between access points. If an access switch is your core layer, no need for a controller. Mount the access point on a camera tripod to ascertain best position in room. RF signals will scatter off pipes.
The AP equipment should have a dashboard, which I gather from your dB comment. So move the AP around on the tripod in one room while keeping it fixed in the other. See how it affects the dB rating. Also, walk around the room with your laptop or download an app to your Android or iPhone for measuring wireless signal (I’ve got one on my iPhone) and check the signal. Perform a stress test between AP’s and ping Cisco.com to check ms return time of ICMP packets.
Also, check for interference from various sources: microwave oven, wireless telephones, radar - anything. The amount of source interference out...