Speed issues on RouterBOARD cAP-2nD

Hello, We have MikroTik RouterBOARD cAP-2nD (ceiling Access Point) and 100 Mbit/s internet connection.
We have 30 clients connected to ap and shared internet between theme. Unfortunately download and upload speed is worse even connect with one client to AP!
Download and upload gets 40 mb/s.
We can download 100mb/s from cap2nd ether port!
Our clients support 802.11b/g/n.
We tried a few different configs that we found… Changing channel-width, rates, disabling firewall didn’t help.also Spectrum is clean, Any suggestions?

Hi,
I’d recommend checking the data rates of clients that are connected and if they support 40Mhz channel-width. Also make sure the frequency you are using is not overcrowded through freq. usage or spectral history