Plutonium

Hello, I regularly play on ztavern servers on plutonium bo2 zombies. Normally my ping is 50 but since tuesday evening something weird has been happening. On half of the servers I have my normal ping, on the other half i get anything between 300 and 450. I really don't know what could be the reason. I am the only player on the server experiencing something like that and the internet on my side is good. I get normal ping on all other plutonium servers and other games. All of the Z-Tavern servers are located in Europe so it shouldnt be a matter of distance because that would affect my ping on all servers and not only half of them. Any ideas what I could do? I've tried resetting my internet multiple times, reintalling bo2 and even plutonium. I kinda ran out of ideas of what I could do.