Mongoose find() returning only one document in production, works normally in development

I have a simple query in mongoose:

var emails = [];
User.find({ subscribed: true })
.exec(function(err, users) {
    console.log(users)
    if (err) {
        console.log(err)
    }

    async.forEach(users, function(user, callback) {
        if (emails.indexOf(user.email) == -1) {
            console.log(user.email)
            emails.push(user.email)
            send(post, user.email)
            callback()                  
        }
    })
})

There are 3 Users. When I run this query, only one is ever returned and it's always the same User. When I replace the line User.find({ subscribed: true }) with User.find({}), all accounts are returned, however when the User are printed in the console they all clearly show subscribed: true.

Additionally, the query executes as expected on my local development environment. The issue only occurs on my production server. Could this be a mongo/mongoose/Node version issue?

via Cameron Sima