limited connected devices

I have had my Asus ac3200 for a year and a half and it has worked well for what I had connected to it..3 SSIDs, 1 for each band and 1 guest network. I have 2 tablets, 3 phones, and 2 laptops on 1 5ghz band it's on SSID. On the other 5ghz band on it's own SSID I have 2 TV's, 2 game consoles, 2...