Wireless network goes down in office network ?need help to resolve it

Dear Friends,

Facing issue with wireless network dropping every 5-6hrs systems showing limited access and it hampering work.request you guys to help me out

My organisation network goes like this
Wan ISP to LAN range starting 192.168.1.1 to 255(DHCP) and connected 2TPLINK N300 and TPlink 450N wireless router as access points transmitting same ip range and got same ssid /password but my network goes down every 5-6hrs and shows limited connectivity on network checked all lan point and connected to other lan ports and changed lan cables but still my wireless network goes down …increased Lease time to 12hrs not getting sorted out.we got 40laptops and also mobile connected to wireless

Kindly help asap …