na it cant be possible, even when buying 10,000RPM drive i write to WD's technical support as if I Require hard drive cooler.
to that they said, absolutely NOT. and I have even touched my hard drives while running, less than warm temperature. so how come it can increase 10C?
one possibility could be, that there is no other hole(s) for ventilation in your casing, and you have a fan right in front of hard drives, where the air is entering the casing passing through hard drives making it warmer.
but still 3-4 C could have been increased, not 10C