Poor WiFi performance on mobile devices orbi rb30

Hi I am getting more and more hassle from my family about how slow the WiFi is. I have 200mb fibre and a RB30 kit. Static devices ( desktops, Sonos, virgin boxes and TVs are all fine and rock solid. Anything that moves (a variety of iOS and Android phones and tablets) is awful even though the device says it has a strong signal. The router and satalitte are about 30' apart through 2 solid walls.

Any suggestions??