Hello and Welcome! What a beautiful Alexandrine. I'm sorry he's having a problem. Hopefully some other Alexandrine owners will be along soon. I have a Cherry-headed conure who had bald spots in front of both of his eyes similar to this about one year ago. It seems to me that for my Opie, it was because he kept scratching his face. The vet said that it was probably due to his hormones. For Opie, I'm upping his mistings and baths at the moment in hopes of keeping his hormonal itchy/scratchies at bay.
To really know what is going on, I would always recommend a visit to your vet.