Hi,
In the 4th block you have this:
<h4 class="panel-title"> <a class="collapsed collapse-titles" role="button" data-toggle="collapse" data-parent="#accordion" href="#collapseThree" aria-expanded="false" aria-controls="collapseThree"> SHOCK FUSE </a> </h4>
The href and aria controls should be collapseFour and not collapseThree.
e.g.
<h4 class="panel-title"> <a class="collapsed collapse-titles" role="button" data-toggle="collapse" data-parent="#accordion" href="#collapseFour" aria-expanded="false" aria-controls="collapseFour"> SHOCK FUSE </a> </h4>