Cannot get maximum wifi connection

Hi,

I recently purchase the AX1800 WiFi Router (RAX20). In the iPhone and iPad app I can't seem to have any device connected with a maximum connection (3 bars). I only get one or two bars, even for a device such as my PlayStation 4 that is like three meters away from the router. I tried changing the channels for both the 2.4 Ghz and 5Ghz band, but it doesn't seem to change anything at all. I also enabled OFDMA for both bands. 

I have a few devices connected to the router:

– 1 iPhone SE 2nd generation

– 1 Apple Watch SE

– 1 iPad

– 1 MacBook Pro

– 1 Apple TV

– 4 Homepod mini

– 1 PlayStation 4

– 1 Nintendo Wii U

– 1 Nintendo Switch

– 1 Samsung TV

– 1 Yamaha audio receiver

Is there anything I can do to have a better connection? The WiFi works, it's just I should be able to have a better connection in my 910 square feet condo.

Thanks!

Ben