Query causing Database lock problem (php/Mysql)
SELECT 
    u.username, 
    u.email, 
    u.created_at, 
    p.firstname, 
    p.lastname, 
    p.address, 
    p.address_2, 
    p.city, 
    p.country, 
    p.state, 
    p.zip, 
    p.phone, 
    p.phone_2, 
    u.last_ip, 
    u.last_login_at, 
    u.auto_login, 
    u.registration_page,
    s.product_name
    FROM
    users AS u
        Left Join subscriptions AS s ON u.id = s.user_id
        Left Join profiles AS p ON u.id = p.user_id
        LEFT JOIN goal_sheets AS gs ON u.id = gs.user_id
        LEFT JOIN sheet_user_popup_not_adam AS supna ON u.id = supna.user_id
    where u.registration_page='Chris_Cleanse' and
        s.expired=TRUE and
        gs.user_id IS NULL and
        supna.user_id IS NULL
    ORDER BY u.id DESC


You can transform the subqueries into left joins and check for IS NULL in where conditions. MySQL performs better on joins than on subqueries.

Have you set appropriate indexes on your tables? Otherwise this should be done too. (Indexes on subscriptions.user_id, profiles.user_id, goal_sheets.user_id and sheet_user_popup_not_adam.user_id should exist as minimum.)