Estoy usando elnth-child selector para agregar imágenes de fondo para diferentes íconos sociales. Sin embargo, todos los iconos parecen iguales. ¿Qué estoy haciendo mal?

.social-logo {
    display: inline-block;
    width: 24px;
    height: 24px;
    transition: background-image .2s;
}

#social-links div:nth-child(1) {
    background-image: url('https://mysql-raigovind93.c9users.io/Cally%20Dai//img/footer/logo-linkedin.svg');
}

#social-links div:nth-child(1):hover {
    background-image: url('https://mysql-raigovind93.c9users.io/Cally%20Dai//img/footer/logo-linkedin-copy.svg');
}

#social-links div:nth-child(2) {
    background-image: url('https://mysql-raigovind93.c9users.io/Cally%20Dai//img/footer/logo-dribbble.svg');
}

#social-links div:nth-child(2):hover {
    background-image: url('https://mysql-raigovind93.c9users.io/Cally%20Dai//img/footer/logo-dribbble-copy.svg');
}

#social-links div:nth-child(3) {
    background-image: url('https://mysql-raigovind93.c9users.io/Cally%20Dai//img/footer/logo-email.svg');
}

#social-links div:nth-child(3):hover {
    background-image: url('https://mysql-raigovind93.c9users.io/Cally%20Dai//img/footer/logo-email-copy.svg');
}

#social-links div:nth-child(4) {
    background-image: url('https://mysql-raigovind93.c9users.io/Cally%20Dai//img/footer/logo-insta.svg');
}

#social-links div:nth-child(4):hover {
    background-image: url('https://mysql-raigovind93.c9users.io/Cally%20Dai//img/footer/logo-insta-copy.svg');
}

<div id="social-links">
  <a href=""><div class="social-logo"></div></a>
  <a href=""><div class="social-logo"></div></a>
  <a href=""><div class="social-logo"></div></a>
  <a href=""><div class="social-logo"></div></a>
</div>