@ReakChaos Good day,
Thanks for your photo, the powerline rate was affected and become slow by possible powerline noise or interference around the home.
You could follow this instruction and remove the things that may affect the power environment:
https://www.tp-link.com/support/faq/409/
( AC power adapters or electrical devices with a motor such as air-conditioners, washing-machines, electric-fans etc., put them far away from powerline devices)
If it recommended to put powerline units in the same room or in a power strip and check the powerline rate will become slow or not?
Please test the powerline units in a different location or house if possible.