Looking for suggestions on optimizing server, lag too much

Hey there, I built a Quilt SMP server for some friends and when any more than 2 people on it starts to lag like crazy. The TPS and MSPT is looking bad but im having a tough time understanding the info and trying to read this spark report better to figure out a better plan of action. Any guidance would be greatly appreciated.
https://spark.lucko.me/OIUZjk4aGP