Update GUI on variable change

Question

I am making a space shooter and in the bottom left corner I have my stat displayed in GUI. The onGUI is I think only called when the game starts because when I change variable in a script it should change the GUI to since it gets its numbers from that script!

private void OnGUI()
{
    Vector2 targetPos = Vector2.zero;
    ////draw Armor
    //VitalStat armor = GetStat(StatType.Armor) as VitalStat;
    //VitalStat health = GetStat(StatType.Health) as VitalStat;
    //VitalStat shield = GetStat(StatType.Shield) as VitalStat;
    //VitalStat energy = GetStat(StatType.Energy) as VitalStat;

    if (GetComponent<Ship>() != null)
    {
        targetPos = new Vector2(95, Screen.height - 65);

        int row = 0;
        if (Armor.CurrentValue > 0)
        {
            GUIUtil.DrawBar(targetPos, 150, 15, row, Armor.CurrentValue, Armor.Value, "Armor");
        }
        else
        //draw Hp
        {
            GUIUtil.DrawBar(targetPos, 150, 15, row, Health.CurrentValue, Health.Value, "Health");
        }
        //draw Shield
        if (Shield.Value > 0)
        {
            row++;
            GUIUtil.DrawBar(targetPos, 150, 15, row, Shield.CurrentValue, Shield.Value, "Shield");
        }

        //draw energy
        if (Energy.Value > 0)
        {
            row++;
            GUIUtil.DrawBar(targetPos, 150, 15, row, Energy.CurrentValue, Energy.Value, "Energy");
        }
    }
    else if (GetComponent<Enemy>() != null)// && _hitTimer > Time.time
    {
        targetPos = Camera.main.WorldToScreenPoint(transform.position);

        int row = 0;
        //draw Shield
        if (Shield.CurrentValue > 0)
        {
            GUIUtil.DrawBar(targetPos, row, Shield.CurrentValue, Shield.Value, "Shield");
        }
        else if (Armor.CurrentValue > 0)
        {
            GUIUtil.DrawBar(targetPos, row, Armor.CurrentValue, Armor.Value, "Armor");
        }
        else
        //draw Hp
        {
            GUIUtil.DrawBar(targetPos, row, Health.CurrentValue, Health.Value, "Health");
        }

        //draw energy
        if (Energy.Value > 0)
        {
            row++;
            GUIUtil.DrawBar(targetPos, row, Energy.CurrentValue, Energy.Value, "Energy");
        }
    }
}

This is where I draw my GUI.

As you can see it gets Armor.Currentvalue and when I change that number the GUI doesn't change does somebody know why or how I can fix it?

UPDATE

This is the stat that keeps track of the health.

public VitalStat Health = new VitalStat() { Type = VitalStatType.Health };

A VitalStat has this:

[HideInInspector]
    public float CurrentValue;
    [HideInInspector]
    public bool ShouldRegenerate = true;
    public VitalStatType Type;
    public StatType RegenerationRate;
    public StatType RegenerationStartDelay;


    private Stat _rate;
    private Stat _delay;
    private float _regenDelayTimer = 0;

This is how the current value gets calculated:

if (ShouldRegenerate && Time.time > _regenDelayTimer && _rate != null)
            {
                CurrentValue = Mathf.Min(Value, CurrentValue + (_rate.Value * Time.deltaTime));
            }

This is the value:

protected float _value;
    public virtual float Value { get { return _value; } }

And the value gets sets by the basevalue:

    public virtual void Init(StatManager statMngr)
        {
            statManager = statMngr;
    
            _value = BaseValue;
            CalculateStatValue();
        }

And the basevalue is set here where I change my health input:

if (!string.IsNullOrEmpty(val))
                    {
                        try
                        {
                            float intVal = Convert.ToSingle(val);
                            target.BaseValue = intVal;

                            //Safe to Database!
                        }
                        catch (Exception e)
                        {
                            Debug.Log("Invalid value " + e.Message);
                        }
                    }

I hope this clarify's it a little bit