Unusually high ram usage without nothing running 8gigs

hi so I got back home and I forgot to turn off my pc, I just went back to it, and I suddenly realized that its kind of slow and video playback, tabs are freezing.

So I checked out system resources and I found out that my firefox takes about 6gigs of ram and Im close to max out 14,6gb /16gb ram so I closed all the apps running, checked all the services there was nothing running and it still was consuming those 8gigs of ram. Im wondering what might be cause of this because when I restarted the pc( took battery out and held the power button for some seconds) then it was back to usual 1gb + something without running anything. When I was using win I found backdoor on my pc that I think could have been planted physically, there was significantly lower performance that came with it, and working disk when the pc was not used( old hdd indicating light was crazy) it was a rat. Im wondering if this might have to do something with it ( IF new backdoor might have been installed when I was away and this caused it) my usb hdds were also quite hot. but they were close to fan. I use x230 thinkpad 16gb ram I would be very grateful for any help and clarification in this :)

I have not found processes running or services running/apps that would consume such a high amount of ram in that time, could this be some kind of manjaro error ? Im not using hybernation/sleep at all, firewall is set to block incoming connections allow outgoing connections.