N300 WIFI slow

I have a Netgear N300 WIFI Cable Modem Router (Model No. C3000) with a 75Mbit internet speed from Xfinity. When wired, I reach speeds in the range between 90~100Mbit but when I am connected to the WIFI network I only reach speeds between 20~25Mbit. Speed tests have been performed on speedtest.net and on the Xfinity speed test website. Please note that I have disconnected any other devices from the network, have no other devices that may interrupt the signal and performed the speed tests on WIFI with a 6 foot distance from the modem/router.

I have contacted Xfinity twice and they ran me through some troubleshooting but to no avail. I tried factory resetting the modem but the problem persists. Browsing through the forums I saw people with similar issues who sometimes may and sometimes may not have been resolved. I tried turning off WMM, tried different channels and adjusting the CTS/RTS Tresholds but it does not produce any results.

I ran out of options and finally decided to post my issue on the forums. Thank you in advance for any suggestions and I will continually check the site for any solutions.