Z-index not working with my animation

The following code (html and css) is driving me crazy ... jsfiddle link

How can I use z-index (or whatever) so that the 3 circles are always visible. With blue this is fine, but yellow and red hide the circle on the left.

Thanks in advance for your help!

<div id="rSociaux" class="col-md-6 noSpace">
<a href="http://www.facebook.com/lesdieuxduvin" target="_blank" id="bg-fb" class="tile-share">
    <div  class="social-color-bg fb"></div>
    <svg class="ontop" height="100" width="100">
        <circle cx="50" cy="50" r="20"  fill="blue" />
    </svg>
</a>
<a href="http://www.twitter.com/lesdieuxduvin" target="_blank" class="tile-share">
    <div class="social-color-bg twitter"></div> 
    <svg class="ontop" height="100" width="100">
        <circle cx="50" cy="50" r="20"  fill="yellow" />
    </svg>
</a>
<a href="http://www.twitter.com/lesdieuxduvin" target="_blank"  id="bg-li" class="tile-share">
    <div class="social-color-bg linkedin"></div> 
    <svg class="ontop" height="100" width="100">
        <circle id="svgLi" cx="50" cy="50" r="20"  fill="red" />
    </svg>
</a>

      

        
        
        
      

    

CSS

#rSociaux {
background-color: #a55fa2;
}

.ontop {
position: relative;
z-index: 10;
}

.tile-share {
display: inline-block;
position: relative;
left: 33%;
-webkit-transform: translateX(-50%) translateY(-0%);
-moz-transform: translateX(-50%) translateY(-0%);
-ms-transform: translateX(-50%) translateY(-0%);
-o-transform: translateX(-50%) translateY(-0%);
transform: translateX(-50%) translateY(-0%);
}

#rSociaux {
overflow: hidden;
}

#rSociaux svg {
position: relative;
z-index: 1000; }

#rSociaux .social-color-bg {
pointer-events: none;
position: absolute;
border-radius: 100%;
top: 50%;
left: 50%;
-webkit-transform: translateX(-50%) translateY(-50%);
-moz-transform: translateX(-50%) translateY(-50%);
-ms-transform: translateX(-50%) translateY(-50%);
-o-transform: translateX(-50%) translateY(-50%);
transform: translateX(-50%) translateY(-50%);
-webkit-transition: 1s;
-moz-transition: 1s;
-o-transition: 1s;
transition: 1s;
}

#rSociaux .social-color-bg.fb {
background: blue;
}

#rSociaux .social-color-bg.twitter {
background: yellow;
}

#rSociaux .social-color-bg.linkedin {
background: red;
}


#rSociaux .tile-share:hover .social-color-bg {
width: 100% !important;
height: 100% !important;
-webkit-transform: scale(20);
-moz-transform: scale(20);
-ms-transform: scale(20);
-o-transform: scale(20);
transform: scale(20);
}