the latency is the average delay time between an AP and connected clients. Latency issues are more often in 2.4 Ghz since that band is usually more interfered since only 3 non-interfered channels.
There are different approches to fix it, I would recommend,
1. Try to find out if there are any WiFi or non-WiFi (microwave ovens, DECT phones, baby monitor, jammer devices from nearby police stations, etc.) devices around the APs. If so try to disconnect them and see if It makes a difference.
2. Test fixing the channels on 2.4 Ghz band to 1, 6 or 11. Usually Ruckus uses background scanning to select the most appropriate channels dynamically. There's an alternative method which is faster , ChannelFly, but It takes more resources from the AP.
3. If the above does not help we would need to reposition the APs away from noise.