Applet not appearing full

Here’s another variation on your layout. Using @Andrew’s tag-in-source method, it’s easy to test from the command line:

$ /usr/bin/appletviewer HomeApplet.java

// <applet code="HomeApplet" width="400" height="200"></applet>
import java.awt.BorderLayout;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JApplet;
import javax.swing.JButton;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTabbedPane;
import javax.swing.JTextField;
import javax.swing.SwingUtilities;

public class HomeApplet extends JApplet {

    @Override
    public void init() {
        try {
            SwingUtilities.invokeAndWait(new Runnable() {

                @Override
                public void run() {
                    createGUI();
                }
            });
        } catch (Exception e) {
            e.printStackTrace(System.err);
        }
    }

    private void createGUI() {
        JTabbedPane tabbedPane = new JTabbedPane();
        tabbedPane.addTab("Rcon1", new RconSection());
        tabbedPane.addTab("Rcon2", new RconSection());
        this.add(tabbedPane);
    }

    private static class RconSection extends JPanel implements ActionListener {

        private static final String TEST_COMMAND = "test";
        private static final String CLEAR_COMMAND = "clear";
        private JTextField ipText = new JTextField();
        private JTextField portText = new JTextField();
        private JTextField rPassText = new JTextField();

        public RconSection() {
            super(new BorderLayout());
            JLabel ip = new JLabel("IP");
            JLabel port = new JLabel("Port");
            JLabel rPass = new JLabel("Rcon Password");
            JButton testButton = new JButton("Test");
            testButton.setActionCommand(TEST_COMMAND);
            testButton.addActionListener(this);
            JButton clearButton = new JButton("Clear");
            clearButton.setActionCommand(CLEAR_COMMAND);
            clearButton.addActionListener(this);
            JPanel panel = new JPanel(new GridLayout(3, 2));
            panel.add(ip);
            panel.add(ipText);
            panel.add(port);
            panel.add(portText);
            panel.add(rPass);
            panel.add(rPassText);
            JPanel buttons = new JPanel(); // default FlowLayout
            buttons.add(testButton);
            buttons.add(clearButton);
            add(panel, BorderLayout.NORTH);
            add(buttons, BorderLayout.SOUTH);
        }

        @Override
        public void actionPerformed(ActionEvent e) {
            System.out.println(e);
        }
    }
}