If you only want to set the title of the button you've clicked on, get rid of the for loop,
- (IBAction)switchAction:(UIButton *)sender {
if (sender.tag == 0) {
[sender setTitle:@"1st Button" forState:UIControlStateNormal];
} else if (sender.tag == 1) {
[sender setTitle:@"2nd Button" forState:UIControlStateNormal];
} else if (sender.tag == 2) {
[sender setTitle:@"3rd Button" forState:UIControlStateNormal];
}