Powerline download speeds drop dramatically after adding extra adapter

I have a PowerLINE 1000 + WiFi (PLW1000) set up that I have been using for over a year that has consistently provided 85Mbps download speeds. I recently received a PLP1200 set of adapters. After following the direction to add one of the modules to my existing setup, my download speeds have dropped to 3Mbps on the new module as well as between the existing modules.  Even removing the new module from the outlet, my existing modules are stuck at no greater than 3Mbps.  Pick-a-plug indicators are greeen on all modules. Interestingly, the upload speeds on all modules (new+old) are in the same range they were before adding in the new module: ~30Mbps.

Are there additional troubleshooting steps I can take to figure out why speeds have dropped?  Is this expected behavior if there are more than two modules in a network?