Well gues i'm part of the club now , after reading all the posts decided to give it a good inspection here's what I found with just under 100 flights ...
I'm no expert but, you may be able to pop the lens out to learn more about the crack and what's behind it. It may pay you to watch a P4 disassembly YouTube video. I know it's easy and have done it before a ways back.
Send it in for warranty repair. They replaced my P4 because of a cracked body with no crashes. However, don't have any stickers installed on the craft, or wraps installed. That will void the warranty.
NewI noticed some cracks on diagonally opposite motor mounts. Fixed them by taping along the arms up to the motor with 3M Scott 897 Filament tape. Have flown 20 hours since then without any problems