Reset Counter on OnJoinedRoom help

Hello, i have 2 coutners which show the score of both players, if a new player joins i want to reset the score for both players (reset the "new player" score is easy) but the player that already is connected keeps the scores up, how can i reset the scores on both sides if a new player joins?

Code (csharp):

1. public class Score: MonoBehaviour {
2.     public int score;
3.     void Update() {
4.          
5.        
6.         GetComponent<TextMesh>().text= score.ToString();
7.  
8. }
9.     void OnPhotonSerializeView(PhotonStream stream, PhotonMessageInfo info)
10.     {
11.         if(stream.isWriting)
12.         {
13.             stream.SendNext(score);
14.  
15.         }
16.         else
17.         {
18.             score=(int) stream.ReceiveNext();
19.  
20.         }
21. }
22. }

thats my current code, but it doesnt affect the players which were in the room when the new player joined