@Phaedrux
Thank you very much for the response.
I think you may be onto something.
The router type is an ASUS RT-AC88U, and there is a way to disable the maybe not so "Smart Connect" feature. This allows for only the 2.4 or 5 Ghz band. I set it to 2.4, and all three printers connected in short order. Gonna call it quits for tonight, but I will have to do some reset testing very soon here.
Hopefully, I can call this solved!
In case anyone wants to know the config...
; Network M552 S1 P"mySSID" ; enable network M586 P0 S1 ; enable HTTP M586 P1 S0 ; disable FTP M586 P2 S0 ; disable Telnet