Weird lag problem

so us 3 friends first played with my server for like 1-2 week without no issue. when we made everything and bored because of it we then played on my friend(1)'s server. we played that 1month i think im not sure. and then we wanted to play on my friend(2)'s server. but his server was too laggy. we tought it would last for like just 1-2 minutes but it didnt got fixed. then we tried if the whole aternos server is lagging but no only my friend(2)'s server. we restarted relogged. nothing worked. it would be awesome if u guys could help about this.