How about achieving this using only HTML attribute 'disabled'
<form>
<fieldset disabled>
<div class="row">
<input type="text" placeholder="">
<textarea></textarea>
<select></select>
</div>
<div class="pull-right">
<button class="button-primary btn-sm" type="submit">Submit</button>
</div>
</fieldset>
</form>
Just by putting disabled in the fieldset all the fields inside of that fieldset get disabled.
$('fieldset').attr('disabled', 'disabled');