Exactly as aurelius says - ventilate them, as above and/or in detail as I did here. In fact the case itself provides a nice chimney effect to help direct the airflow to keep the HD nice and cool (32-36C as shown in this snap of some of my drives using ‘Clear Disk Info’)
69C (156.2F) sounds terribly hot (like twice as hot 
, hopefully they were not damaged in some way that makes them susceptible to failure or so they will run hot for regardless of proper venting.