To reproduce:
1. Click the button 'set font'
Result: font won't change
Expected: font should increase

import javafx.application.Application;
import javafx.application.Platform;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.PasswordField;
import javafx.scene.control.TextArea;
import javafx.scene.control.TextField;
import javafx.scene.layout.Pane;
import javafx.scene.layout.VBox;
import javafx.scene.text.Font;
import javafx.stage.Stage;

public class TextFieldApp extends Application {

    public static void main(String[] args) {
        launch(args);
    }

    @Override
    public void start(Stage stage) throws Exception {
        stage.setScene(createScene());
        stage.show();
    }

    private Scene createScene() {

        final TextField textField = new TextField("2/2/2000");
        final PasswordField passwordField = new PasswordField();
        final TextArea textArea = new TextArea("Test");

        Button setFont = new Button("Set font");
        setFont.setOnAction(new EventHandler<ActionEvent>() {
            @Override
            public void handle(ActionEvent actionEvent) {
                new Thread(new Runnable() {
                    @Override
                    public void run() {
                        Platform.runLater(new Runnable() {
                            @Override
                            public void run() {
                                textField.setFont(new Font(20));
                                passwordField.setFont(new Font(20));
                                textArea.setFont(new Font(20));
                            }
                        });
                    }
                });
            }
        });

        VBox root = new VBox(5);
        root.getChildren().addAll(textField, passwordField, textArea, setFont);

        return new Scene(root, 1200, 800);
    }
}