Ping spikes / bad latency during high-traffic times

I live in an apartment in a midsized city. The apartment is primarily leased by college students, so when I moved here in the summer most people were presumably at home and there wasn't much traffic on the internet. I started with the 400mbps download plan and everything was dandy. Starting early September, I began noticing ping spikes in the evening and it got worse and worse until late December (winter break for the college students) and everything was great again. I'm on ethernet, and when running a ping test on ping-test.net, I see my ping spiking from 40 to high triple digits every 5 or so seconds. I have had 2 techs visit and they just test my router and say everything looks dandy. The first tech recommended I upgrade my speed so I got the 800mbps download package back in October and I didn't notice any difference. I think one of them had the maintenance team come look at the building but I haven't heard anything. I got a new coax and ethernet cable and I've been playing video games with this setup for years and haven't had this problem until September of last year. I'm open to any suggestions or tests that would find prove what is at fault because I'm certain its something on xfinity's end.