WiFi routers have a setting called WiFi channel.
Most appropriate values to be put is either 1, 6 or 11. Because only these 3 values are non-interfering with each other.
You can see this using a simple mobile app called WiFi Analyzer.
Open this app and it will show you the channels and signal strength of all nearby WiFi routers .
Ensure that you get the 3 non-intersecting domes in your premise as seen below by selecting either of 1,6,11 channel numbers. Unfortunately by default all APs/Routers have set this to auto which causes interference with other channels. Nearer the routers, stronger the interference effect, so even if you do this on all routers in your office premise it should be good enough.
Try to get as close to IDEAL as possible by following this on all your WiFi APs/routers.
This can make difference between 2 Mpbs and 70 Mbps.
This problem is more pronounced in 2.4Ghz WiFi compared to 5Ghz, because 5Ghz has lot many non-interference channels available.
Notice how cleanly non-intersecting all 3 domes are.
There is no dome at all due to all intersecting channels.