Mysql2::Error::ConnectionError: Access denied for user 'myapp'@'localhost' (using password: YES)のエラー

railsを用いてwebサービス開発中です
完成したwebサービスをherokuを用いてデプロイしました

サービスページをみてみると、初期データであるseedデータが反映されていなかったので、以下のサイトを参考にしてseedデータを投入しようとしたとこmysqlのエラー

参考サイト
https://qiita.com/Masanori_N/items/a9b4ae00e3e153ecb2e6

rails db:seed_fu RAILS_ENV=production 

== Seed from /Users/username/Shinshu-Fiber/db/fixtures/masters.rb
rake aborted!
Mysql2::Error::ConnectionError: Access denied for user 'Shinshu_Fiber'@'localhost' (using password: YES)

上記のmysqlエラーを調べたところ以下のサイトが参考になったので、手順通り進めパスワードを変更しましたが、またしても同じエラーが発生してしまいました

参考サイト
https://qiita.com/naota7118/items/b62d71484e21d6739d68

database.yml

# MySQL. Versions 5.5.8 and up are supported.
#
# Install the MySQL driver
#   gem install mysql2
#
# Ensure the MySQL gem is defined in your Gemfile
#   gem 'mysql2'
#
# And be sure to use new-style password hashing:
#   https://dev.mysql.com/doc/refman/5.7/en/password-hashing.html
#
default: &default
  adapter: mysql2
  encoding: utf8mb4
  pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>
  username: root
  password: password
  socket: /tmp/mysql.sock

development:
  <<: *default
  database: Shinshu_Fiber_development

# Warning: The database defined as "test" will be erased and
# re-generated from your development database when you run "rake".
# Do not set this db to the same as development or production.
test:
  <<: *default
  database: Shinshu_Fiber_test

# As with config/credentials.yml, you never want to store sensitive information,
# like your database password, in your source code. If your source code is
# ever seen by anyone, they now have access to your database.
#
# Instead, provide the password as a unix environment variable when you boot
# the app. Read https://guides.rubyonrails.org/configuring.html#configuring-a-database
# for a full rundown on how to provide these environment variables in a
# production deployment.
#
# On Heroku and other platform providers, you may have a full connection URL
# available as an environment variable. For example:
#
#   DATABASE_URL="mysql2://myuser:mypass@localhost/somedatabase"
#
# You can use this database configuration with:
#
#   production:
#     url: <%= ENV['DATABASE_URL'] %>
#
production:
  <<: *default
  database: Shinshu_Fiber_production
  username: Shinshu_Fiber
  password: password

なにか解決策はあるでしょうか、また間違っている点などございましたらご教授お願いいたします