C# JSON file deserialized into multiple objects

This is my first question on Stackoverflow. I am learning C# and I build a simple bank console app in C#. A small menu was created where one of the options is to allow the user create a bank account and it gets saved in a json file.

A sample of the saved user inputs into the json file is as such:

{
    "FirstName": "Ari",
    "LastName": "Man",
    "Pin": 1122,
    "Balance": 400.0
}
{
    "FirstName": "Tari",
    "LastName": "Man",
    "Pin": 3434,
    "Balance": 566.89
}
{
    "FirstName": "Mari",
    "LastName": "Man",
     "Pin": 5656,
    "Balance": 677.0
}

My code is:

using System;
using System.Collections.Generic;
using System.IO;
using System.Runtime.Remoting;
using Newtonsoft.Json;

namespace BankApp
{
    public class Program
    {
        public static void Main(string[] args)
        {
            string selection;
            //int _initPin;
            double newBalance;

            //create bank object
            Accounts bank = new Accounts();

            //display menu
            while (true)
            {
                Console.WriteLine("=======================================");
                Console.WriteLine("Welcome to Banko - your online Bank App");
                Console.WriteLine("=======================================\n");
                Console.WriteLine("1. Account Balance\n");
                Console.WriteLine("2. Open an account\n");
                Console.WriteLine("3. Withdraw\n");
                Console.WriteLine("4. Deposit\n");
                Console.WriteLine("5. Exit\n\n");

                Console.WriteLine("Select an option:\n ");
                selection = Console.ReadLine();

                if (selection == "5")
                {
                    Console.WriteLine("Thank You! Hope to see you soon");
                    Console.ReadLine();
                    break;
                }
                else
                    switch (selection)
                    {
                        case "1":
                            Console.WriteLine(Deserialize());
                            break;

                        case "2":
                            Console.WriteLine("Enter your first name: ");
                            bank.FirstName = Console.ReadLine();
                            Console.WriteLine("Enter your last name: ");
                            bank.LastName = Console.ReadLine();
                            Console.WriteLine("Enter a new new PIN: ");
                            bank.Pin = int.Parse(Console.ReadLine());
                            Console.WriteLine("Enter starting balance: ");
                            bank.Balance = double.Parse(Console.ReadLine());
                            break;

                        case "3":
                            newBalance = bank.Withdraw();
                            Console.WriteLine("Your current balance is: {0}", newBalance + Environment.NewLine);
                            break;

                        case "4":
                            newBalance = bank.Deposit();
                            Console.WriteLine("Your current balance is: {0}", newBalance + Environment.NewLine);
                            break;
                    }
            }


            //serialize JSON file and write to json file
            string filePath = @"C:\Users\shakazul\source\repos\BankApp\accounts.json";
            string output = JsonConvert.SerializeObject(bank, Formatting.Indented);
            File.AppendAllText(filePath, output + Environment.NewLine);
        }

        public static Accounts Deserialize()
        {
            //path to JSON file and read file
            string filePath = @"C:\Users\shakazul\source\repos\BankApp\accounts.json";
            string jsonResults = File.ReadAllText(filePath);

            //Deserialize the JSON file to an object
            Accounts results = JsonConvert.DeserializeObject<Accounts>(jsonResults);
            return results;
        }
    }
}

My class is:

namespace BankApp
{
    public class Accounts
    {
        public string FirstName { get; set; }
        public string LastName { get; set; }
        public int Pin { get; set; }
        public double Balance { get; set; }

        public Accounts()
        {
            this.FirstName = FirstName;
            this.LastName = LastName;
            this.Pin = Pin;
            this.Balance = Balance;
        }
   
        public double Deposit()
        {
            double deposit;
            double newBalance;

            Console.WriteLine("Please enter amount to deposit: ");
            deposit = double.Parse(Console.ReadLine());

            newBalance = Balance + deposit;

            return newBalance;
        }

        public double Withdraw()
        {
            double newBalance;
            double withdraw;

            Console.WriteLine("Please enter amount to withdraw: ");
            withdraw = double.Parse(Console.ReadLine());

            newBalance = Balance - withdraw;

            return newBalance;
        }
    }
}

So my issue is that when I was get parse the json file and get the account balance of a certain customer based on the PIN they entered, I get an error

Newtonsoft.Json.JsonReaderException: 'Additional text encountered after finished reading JSON content: {. Path '', line 6, }

So if I had only one entry, I can retrieve the balance value, but more than that and I get the error that happens at:

Accounts results = JsonConvert.DeserializeObject<Accounts>(jsonResults); 

line of the code.

Any help would be greatly appreciated.