Each core will be doing slightly different amounts of work, so yes, you'd expect them to have slightly different temperatures. If you ever find that your cores have *massively* different temperatures then you need to worry about whether your cooler is seated properly / thermal paste applied correctly, but as long as they're within a reasonable margin (say ~ 10%?) of each other there's no worry about the cores being different temperatures.
You'll find the base clocks for most motherboards are subject to tiny fluctuations in frequency - your variation is < 0.003%, which is pretty high tolerance