No, I'm sorry - there is no ability to adjust the brightness of screens individually. It is the nature of some electronic components that there may be some variation and obviously this unit passed the quality control threshold.
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It's not common, but this can happen. Is the unit new or old? Can you post a photo?
The unit was built in 2013. 
left deck
right deck
I don't see enough of a difference to make me believe there's any problem.
The different brightness there is, though little. Can you adjust by a Pioneer technician?
