I will provide all the informations as much as I can. 

Supposed internet speed up/down - 50Mbps up & 100Mbps

I have two SSID's, one is from the router itself which I will denote as WIFI 1 and from powerline adapter as WIFI 2. 

My house is 3 PHASE WIRING. Hence why I bought TL-WPA8630P_KIT as recommended by a staff at a local distributor. Initially, I had stable connection from my powerline adapter for 2 years. However, a few days ago, I have been having unstable connection from my powerline adapter. At first I thought the connection from my router is problematic but I checked and confirmed that the connection from WIFI 1 is working fine(Accurate speed and low ping&jitter). The problem I'm having is coming from my WIFI 2.

The issues are as following; 1) very high ping (refer to picture)

                                              2) red colour powerline LED

So I tried to solve the issue by;  1) checking the main device(the one that has to be connected to the router) but all LED indicators are green.

                                                   2) I tried plugging the secondary adapter into different power outlets on each floor.

                                                   3) I have updated the firmware to the latest version way before this problem occurred.

                                                   4) I have resetted the adapters and paired it again

What I noticed, during the day, the connection is fine and smooth. Both adapters have all green LED indicators and I have very low ping which is great. But when it comes to night time, connection goes crazy. If i leave my computer at idle state(not browsing, gaming etc) I will get below 40ms but if i try to browse something it will rise to 1000ms+. This does not happen before, it started to occur a few days ago. I have ran out of ideas on how to fix this. In dire need of help to resolve this issue. Thank you in advance.