Capistranoデプロイ時、Access deniedエラー

前提・実現したいこと

個人開発アプリのデプロイ作業にて、Capistranoの導入を行なっております。
一通りのコーディングを実装後、deproyコマンド時以下のようなエラーが発生したため、
解消したいです。

発生している問題・エラーメッセージ

Mysql2::Error::ConnectionError: Access denied for user 'growool'@'localhost' (using password: NO)

該当のソースコード

database.yml

<% require 'settings' %>

default: &default
  adapter: mysql2
  encoding: utf8
  pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>
  username: root
  password:
  socket: /tmp/mysql.sock
  host: localhost

development:
  <<: *default
  database: growool_development

test:
  <<: *default
  database: growool_test

production:
  adapter: mysql2
  encoding: utf8
  pool: 5
  database: growool_production
  username: <%= mysql.database_name %>
  password: <%= mysql.database_password %>
  socket: /var/lib/mysql/mysql.sock
  host: localhost

deploy.rb

lock "~> 3.14.0"

set :application, "growool"
set :repo_url, "git@github.com:keisuke-kk/growool.git"
# set :branch, 'master'

# Default branch is :master
# ask :branch, `git rev-parse --abbrev-ref HEAD`.chomp

# Default deploy_to directory is /var/www/my_app_name
set :deploy_to, "/var/www/rails/growool"

set :linked_files, fetch(:linked_files, []).push('config/master.key')
set :linked_dirs, fetch(:linked_dirs, []).push('log', 'tmp/pids', 'tmp/cache', 'tmp/sockets', 'vendor/bundle', 'public/system')
set :keep_releases, 5
set :rbenv_ruby, '2.5.1'
set :log_level, :debug

set :bundle_flags,      '--quiet'
set :bundle_path,       nil
set :bundle_without,    nil

namespace :deploy do
  desc 'Restart application'
  task :restart do
    invoke 'unicorn:restart'
  end

  desc 'Create database'
  task :db_create do
    on roles(:db) do |host|
      with rails_env: fetch(:rails_env) do
        within current_path do
          execute :bundle, :exec, :rake, 'db:create'
        end
      end
    end
  end

  desc 'Run seed'
  task :seed do
    on roles(:app) do
      with rails_env: fetch(:rails_env) do
        within current_path do
          execute :bundle, :exec, :rake, 'db:seed'
        end
      end
    end
  end

  desc 'Config bundler'
  task :config_bundler do
    on roles(/.*/) do
      within release_path do
        execute :bundle, :config, '--local deployment true'
        execute :bundle, :config, '--local without "development test"'
        execute :bundle, :config, "--local path #{shared_path.join('bundle')}"
      end
    end
  end

  after :publishing, :restart

  after :restart, :clear_cache do
    on roles(:web), in: :groups, limit: 3, wait: 10 do
    end
  end
end

before 'bundler:install', 'deploy:config_bundler'

capfile

require "capistrano/setup"

require "capistrano/deploy"

require "capistrano/scm/git"
install_plugin Capistrano::SCM::Git

require 'capistrano/setup'
require 'capistrano/deploy'
require 'capistrano/rbenv' 
require 'capistrano/bundler'
require 'capistrano/rails/assets' 
require 'capistrano/rails/migrations'

Dir.glob("lib/capistrano/tasks/*.rake").each { |r| import r }

gemfile

source 'https://rubygems.org'
git_source(:github) { |repo| "https://github.com/#{repo}.git" }

ruby '2.5.1'

# Bundle edge Rails instead: gem 'rails', github: 'rails/rails'
gem 'rails', '~> 5.2.4', '>= 5.2.4.3'
# Use mysql as the database for Active Record
gem 'mysql2', '>= 0.4.4', '< 0.6.0'
# Use Puma as the app server
gem 'puma', '~> 3.11'
# Use SCSS for stylesheets
gem 'sass-rails', '~> 5.0'
# Use Uglifier as compressor for JavaScript assets
gem 'uglifier', '>= 1.3.0'
# See https://github.com/rails/execjs#readme for more supported runtimes
# gem 'mini_racer', platforms: :ruby

# Use CoffeeScript for .coffee assets and views
gem 'coffee-rails', '~> 4.2'
# Turbolinks makes navigating your web application faster. Read more: https://github.com/turbolinks/turbolinks
gem 'turbolinks', '~> 5'
# Build JSON APIs with ease. Read more: https://github.com/rails/jbuilder
gem 'jbuilder', '~> 2.5'
# Use Redis adapter to run Action Cable in production
# gem 'redis', '~> 4.0'
# Use ActiveModel has_secure_password
# gem 'bcrypt', '~> 3.1.7'

# Use ActiveStorage variant
# gem 'mini_magick', '~> 4.8'

# Use Capistrano for deployment
# gem 'capistrano-rails', group: :development

# Reduces boot times through caching; required in config/boot.rb
gem 'bootsnap', '>= 1.1.0', require: false

group :production, :staging do
  gem 'unicorn'
end

group :development, :test do
  # Call 'byebug' anywhere in the code to stop execution and get a debugger console
  gem 'byebug', platforms: [:mri, :mingw, :x64_mingw]

  gem 'pry-rails'
  gem 'capistrano'
  gem 'capistrano-bundler'
  gem 'capistrano-rails'
  gem 'capistrano-rbenv'
end

group :development do
  # Access an interactive console on exception pages or by calling 'console' anywhere in the code.
  gem 'web-console', '>= 3.3.0'
  gem 'listen', '>= 3.0.5', '< 3.2'
  # Spring speeds up development by keeping your application running in the background. Read more: https://github.com/rails/spring
  gem 'spring'
  gem 'spring-watcher-listen', '~> 2.0.0'

  gem 'pry-byebug'
end

group :test do
  # Adds support for Capybara system testing and selenium driver
  gem 'capybara', '>= 2.15'
  gem 'selenium-webdriver'
  # Easy installation and use of chromedriver to run system tests with Chrome
  gem 'chromedriver-helper'
end

# Windows does not include zoneinfo files, so bundle the tzinfo-data gem
gem 'tzinfo-data', platforms: [:mingw, :mswin, :x64_mingw, :jruby]
gem 'compass-rails', github: 'Compass/compass-rails'
gem 'sprockets'
gem 'devise'
gem 'ed25519'
gem 'bcrypt_pbkdf'
gem 'settingslogic'

application.yml

production:
  mysql:
    database_name: #######
    database_password: #######
    secret_key_base: ###################################

development:

test:

試したこと

・database.ymlにusernameとpasswordを直接書き込んでみました。
エラー内容より、変数にパスワードがうまく適用されていないのではないかと考えたからです。
・EC2にも、localのdatabase.yml等のファイルの内容を書き込みました。
デプロイ時に参照しているのではないかと考えたからです。

補足情報（FW/ツールのバージョンなど）

mysqlのバージョンEC2とlocalの両方で5.7を使用しております。
しかし、アプリケーションの作成時は5.6を使用しており、デプロイ作業の途中で良かれと思い、5.7にアップグレードしました。
そのせいか,
localでrails db:createを実行すると以下のエラーが発生致します。

LoadError: dlopen(/Users/kandakeisuke/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/mysql2-0.5.3/lib/mysql2/mysql2.bundle, 9): Library not loaded: /usr/local/opt/mysql@5.6/lib/libmysqlclient.18.dylib

ご教示頂けますと、幸いです。