if instance_exists(op[3])
{
    with (op[3])
        instance_destroy()
}
if instance_exists(op[4])
{
    with (op[4])
        instance_destroy()
}
if instance_exists(op[5])
{
    with (op[5])
        instance_destroy()
}
if instance_exists(op[6])
{
    with (op[6])
        instance_destroy()
}