@DKS736
Yes you can. As long as the source outlets and the destination outlets are on the same side of your electrical circuit panel.
In fact you can add two PowerLine Decos to your existing Mesh. Or you can purchase TP-Link PowerLine Add-on modules to make two of your existing nodes connect over PowerLine.
Keep in mind that you will not get WiFi fast speed connections. You will be limited to the 1000Mbps Ethernet connections on the Decos.
I have used the TP-LINK TL-PA4010KIT AV600 Nano Powerline 500Mbps Adapter Starter Kit in the past and can attest that you will not see anything over 150Mbps sustained throughput.
I would recommend that you use atleast the TP-Link AV2000 Powerline Adapter with Gigabit ports instead, on Amazon for $119.99
or for $80 more (BEST OPTION) you can add three Deco P9 nodes to your mesh - Amazon $199.00 (on sale today).