Hello there folks,
I was just wondering if y'all could shed some light on something Im baffled over. Apologies if the answer is extremely obvious to you guys but Im confused by it all. I would also love to know if there is a potential fix/improvement for it.

Ill set the scene for you guys:

I recently got myself Fiber Optic (In the Uk this isnt as amazing as US fiber so keep it in your pants). The router is based in my room and with wireless as well as cabled I receive around 55mb/s (still pretty good though right?). However, down my garden, about 10m away from my house is my 'gaming shed'. Its the holy grail of gaming set ups with speakers and tv's and pc's etc etc. However, down the shed I get around 5-10mb/s. To connect to the internet down this shed I use a power-internet passthrough. This is essentially a way to transport internet through the power lines. This is plugged into the router via ethernet and then into the wall socket. Then, down the shed I have another box which receives the internet for me to use. This can transfer 'up to 100mb/s' so i wouldnt have thought this is the issue. From this internet passthrough I have connected a Gigabyte tp-link internet splitter. (Plug one ethernet cable in, get internet for 5 ethernet cables). And this is where I get the highly reduced speeds. No matter what computer or device I use, its all about the same speed. Im only ever using 1 device at a time so its not that im using up all the bandwidth.

Any responses would be much appreciated and I really hope that the above made sense. its a slightly confusing set up to explain without you all being here.

Thank you in advance :D

Sid