This is the last plugin i've installed to my server but since a few days people keep getting kicked for packetflood tick.

Now I dont know if it's this plugin since it says nothing in the console why they would get kicked, but still it's the last plugin I installed and before this it didnt happen, so im wondering if anyone has experienced the same?

Very unlikely to be this. Look for plugins that may be sending console commands to players such as ddraw.

I've increased the tickrate from 300 to 600 and this stops the players getting kicked, however the server still freezes for a few seconds every now and then.

I dont see any errors in the console, how would I troubleshoot this?

Do you have a server console that may have been selected by mistake?