Where/what is my Homeplug slowdown factor?

I have four 5456 plugs, however the problem was the same with two. On my ground floor, I have a fibre modem, Connected to a mandatory Tilgin router that sends a fiber/lan and tv signal from port 4. The cable goes to the first homeplug adapter in the same room. The second one is on an outtake on the first floor, and Connects to the tv fiber Box, and to my Samsung tv. The next adapter is on the next outtake and has one cable going to a PS4 pro and one free.

Then I also have a fourth one in the room next to this, Connected to my computer.

The Tilgin router also has wifi, which is on. I have two wifi speakers Connected to this router, along With two Laptops and two Phones. I have measured the speed on netflix, getting 8mbps Down. On my computer, I get 3 Down 30 up,  and on PS4 Pro I get 12 Down, 5 up.

My fibre speed is 35/35, which I get directly from the router by cable.

I have to surge protectors on the floor, one Connected to the pass through of adapter 3, the other Connected one outtake away from adapter 4.

Please assist, why is my speed so low?

Regards.

#PLA_December