Ethernet 1Gbps - PCB stackup
The datasheet of the PHY comes with a recommended stackup on page 127.
Use that instead of your slightly strange stackup; you don't need to put power on its own plane if it doesn't make layout simpler due to many distributed consumers, which you don't have.
Instead of adding unnecessary power planes, adding dedicated layers for high-speed signals to ease routing and thus allow for better routing at problematic points would make more sense, and that's exactly what the datasheet recommends.