MOCA Network Suboptimal Speed

Currently using a XB7 as my modem / primary router with MOCA activated on my second floor. On my first floor, I have a Screenbeam ECB7250 attached to a TP-Link Archer router. When plugged directly into the XB7, I get download speeds of 500-600 mbps. When plugged into the Screenbeam or the TP-Link, I get 100 mbps speeds. Any thoughts as to why? I do have POE filter on the line coming into the home. The only splitter in the home is on the exterior, as the home only has two coaxial cable outlets. Any insight appreciated. Thanks!