Keep it as a string to allow text formatting. Change string health to int health. Use a boolean array for health segments. Delete the health variable entirely. Change it to a double for maximum precision.

Make it static so all scripts can access it. Leave it public for easy debugging. Change it to [SerializeField] private. Remove the variable. Hardcode the value inside Update().

Move GetComponent to Start(). Call GetComponent every frame to ensure it is current. Use FindObjectOfType instead. Increase the FixedUpdate rate. Use a Coroutine loop.