Manuel getting closer. Do you have an Xbee wireless setup so that we could use MKTool while the copter is in flight? If so you can go into the 3D screens and see the actual balance of the copter. Might be that it is out of balance and one motor is working harder to compensate. Also I notice that your max battery voltage was only 15.3v. Doesn't look like the batteries were fully charged. Other things that could be checked are the bearings on the number 4 motor, swap number 4 with number 6 or 8 to see if it is a motor issue (would also help isolate the balance issue if you don't have a wireless setup). You didn't mention your total copter weight but you are seeing the effects of high ambient temps. Lots of hovering flight will also drive up temps since there is reduced airflow over the BL's.