iOS Lag From Updating Score

I'm working on a 2D platformer where the score is based on the distance traveled by the player. I originally used the update routine to check the player's position and update the uGUI textbox, but I had to make some changes because it caused some substantial lag on all platforms. With these changes, the game now runs fairly smoothly on Android, but it still causes a lot of framerate issues in iOS. I'm having trouble thinking of how to simplify my script further, other than choosing to update every 5 points instead of every point, which is an option I would rather not consider. Can anyone with experience solving this issue give me some advice on how to more efficiently keep the score updated? Here is the script I am currently using:

 IEnumerator UpdateScore()
     {
         while( true )
         {
             if( _isPlaying )
             {
                 _score = (int)player.position.x;
                 scoreText.text = _score.ToString();
             }
 
             yield return new WaitForSeconds( 0.25f );
         }
     }

As you can see, I'm using a coroutine to update the score every 1/4 second, since the player's rigidbody moves at a velocity of 4 m/s.