At this time, the only way to downgrade is to delete your albums, cancel your account, and create a new account with a lower plan with a new email address. For more information about how to do this, please check out this FAQ article.
Please note that if you choose to do this, and sign up for the Musician plan instead of Musician Plus or an Ultimate plan, you will lose the ability to choose a label name, specify release dates, and other great features.
