Flexbox equal width problems - flexbox

Question

Dear fellow stackoverflowers,
I'm having a peculiar problem I can't seem to find the solution for.
I'm trying to apply the width of the largest div to the smaller divs, so that they appear equal in width, through flexboxing. Unfortunately, all the solutions so far have been futile efforts. Do you have any idea why the different divs in the example I've linked to won't display the same width as the largest element? I know the boxes get their width from the content, but I just can't seem to make them behave the way I want.
HTML
<section id="contact" class="wrapper bgfixed">
<div>
<h1>Contact</h1>
<div id="contactholder">
<a href="#">
<div>
<h1 class="icon-mail"></h1>
<h2>EMAIL</h2>
<p>someonesprofessionalemail#gmail.com</p>
</div>
</a>
<a href="#">
<div>
<h1 class="icon-old-phone"></h1>
<h2>TELEPHONE</h2>
<p>39 88 49 92 91</p>
</div>
</a>
<a href="#">
<div>
<h1 class="icon-facebook2"></h1>
<h2>FACEBOOK</h2>
<p>www.facebooooooooooooooooooook.com/snowman</p>
</div>
</a>
<a href="#">
<div>
<h1 class="icon-soundcloud"></h1>
<h2>LOREM IPSUM</h2>
<p>www.loremipsumyesyesyesblahblabhlabh.com</p>
</div>
</a>
</div>
</div>
</section>
CSS
a{text-decoration: none;}
#contact
{
width: 100%;
height: 82vh;
color: whitesmoke;
text-align: center;
display: flex;
align-items: center;
justify-content: center;
background: #34495e;
}
#contactholder
{
display: flex;
justify-content: space-between;
font-size: 80%;
}
#contactholder div
{
flex: 1;
flex-grow: 1;
font-size: 0.5rem;
}
#contactholder div h1
{
padding: 3rem;
letter-spacing: 0;
display: inline-block;
background-image: linear-gradient(white, 1%, #3498db);
border-radius: 100rem;
box-shadow: 0 1px 1px grey;
transition: 0.3s;
margin-bottom: -0.5rem;
}
#contactholder a:hover h1
{
background-image: linear-gradient(white, 1%, #00A4EB);
text-shadow: 0 1px 1px;
}
Hoping for some brilliant minds!
Best wishes,
Lodott1