My headlight plastic cover lenses started to cloud . They were both replaced by the dealer under warranty when I took the 8 in for the recall. Mazda told the dealer to ship the lenses for inspection .
Dealer hasn't come across this problem before. Maybe only certain cars are affected.

 

I used to have the same problem with the plastic headlight lenses on my 10AE Miata. In my case it was due to a buildup of grime on the exterior, and was easily cured with a good dose of Meguiar's #17 Clear Plastic Cleaner followed by #10 Clear Plastic Polish.