Replaced external monitor not recognized MBP 13" Retina
So you're not connecting them exactly the same. You're using two adapters on the Viewsonic (an HDMI-DVI cable and an HDMI-Mini DisplayPort cable daisy-chained together) and one on the old Acer. Now you're trying to connect two via HDMI-Mini DisplayPort cables.

I would suggest trying to connect one of your Acer monitors using a normal HDMI cable to the HDMI port on the right side of the MacBook and the other to the left Thunderbolt port using the HDMI-Mini DisplayPort adapter.