Yes, it's normal for one temperature to be higher than the other. If you take off the side panel you'll notice one of the heatsinks is behind the other. So the first one draws in cooler air from the front intake and then it's expelled to the rear heatsink which draws in some cool air, but mostly the already heated up air from the heatsink in front of it. Therefore the rear heatsink is much warmer, and you'll see that the temperatures are higher.