Thanks for your quick response ! Unfortunately my configuration only works at optimal speeds with the main network at 5Ghz. I only have the guest network at 2.4Ghz because of the printer and my apple...

How can I turn off lan isolation between guest and main SSID ? I need to use AirPrint but my devices are all on the main 5Ghz network while my HP printer can only connect to my 2.4Ghz guest network....