Hi Anjana,
What actions were taken to identify that it was Wi-Fi was causing this issue?
Do you have any endpoint monitoring platform such as Thousand eyes endpoint, 7signal mobile eye etc. which can give visibility into client wireless performance?
Do you have any historic data at the time when the issue happened? such as client debugs, info as how many clients were connected to the AP? Which band user was connected? What was the channel utilization?
If not, I would start with checking whether symptoms are pointing to this bug
https://bst.cloudapps.cisco.com/bugsearch/bug/CSCwa31596
Still I would consider upgrading your WLC to the latest Cisco TAC recommended code, links can be found in my signature.
