Your span element doesn’t begin within the loop. So the other posts after the first don’t get the begin span signal. You need to have :
<?php if ( have_posts() ) : while ( have_posts() ) : the_post(); ?>
<span><?php the_title(); ?></span><br />
I would also put the break after the end span and I’m using the XHTML compliant version of the break tag in this example.