BS3 input-group-addon taller than input - css

Question

I have a footer on my page, with a Newsletter signin form.
The input-group-addon is getting bigger than the input itself ONLY on intern pages, the index page displays correctly, even with the same CSS file, and same footer structure.
Again, same structure, same css...
This is my whole foooter structure:
<!-- FOOTER -->
<footer>
<div class="footer" id="footer">
<div class="container">
<div class="row">
<div class="col-md-2 col-xs-6">
<h3>Tecnologia</h3>
<ul>
<li> Servidores</li>
<li> Programação</li>
<li> Segurança</li>
<li> Backups</li>
</ul>
</div>
<div class="col-md-2 col-xs-6">
<h3>Suporte</h3>
<ul>
<li> Helpdesk </li>
<li> Painel de controle </li>
<li> F.A.Q </li>
<li> Contatos </li>
</ul>
</div>
<div class="col-md-2 col-xs-6">
<h3>Engine</h3>
<ul>
<li> Valores </li>
<li> Missão </li>
<li> Nosso time </li>
<li> Política de uso </li>
</ul>
</div>
<div class="col-md-2 col-xs-6">
<h3>Produtos</h3>
<ul>
<li> Sistemas </li>
<li> Websites </li>
<li> Mídias Sociais </li>
<li> Hospedagem </li>
</ul>
</div>
<div class="col-md-4 col-xs-12">
<h3>Newsletter</h3>
<ul>
<li>
<form action="" method="post" role="form">
<div class="input-group">
<span class="input-group-addon"><i class="fa fa-envelope"></i></span>
<input class="form-control" type="text" id="" name="" placeholder="digite seu e-mail">
</div>
<input type="submit" value="Cadastrar" class="btn btn-large btn-primary" style="margin-top: 10px;" />
</form>
</li>
</ul>
<div>
<i id="social-fb" class="fa fa-facebook-square fa-2x social"></i>
<i id="social-tw" class="fa fa-twitter-square fa-2x social"></i>
<i id="social-yt" class="fa fa-youtube-square fa-2x social"></i>
</div>
</div>
</div>
</div>
</div>
<div class="footer-bottom">
<div class="container">
<p class="pull-left">Copyright © 2017 - ENGINE Sistemas. All rights reserved | ENGINE Sistemas</p>
</div>
</div>
</footer>
The footer is responsive too...
Any help? Thanks!