Odd Medium Editor Behaviour

I have Medium Editors on my site and they work fine. But for some reason below them there seems to be an HTML Preview textarea as well? This is only happening on one of my sites.

Code:

<textarea id="articleContent" name="articleContent" class="form-control" is="dmx-medium-editor" buttons="bold,italic,underline,anchor,quote,unorderedlist,justifyLeft,justifyCenter,justifyRight,justifyFull,removeFormat"></textarea>

Screenshot:

Screen Shot 2018-06-20 at 12.58.23 PM.png1144×316 8.71 KB