Injured head? From What????

Hey everybody.
This season I managed to have 3 cluthes.
The first babies were ok!
Among the babies from clutch 2 & 3 some of them had a mark.
It seems like a scale is missing.
After one shed the mark was better but not enough.
I keep each baby in small plastic boxes and have inside small caps (top of shaving foam) with water and newspaper for bedding.
Do you have any ideas?
http://img251.imageshack.us/img251/2121/pinq.jpg

I wouldn't worry about it, it will probably go away with a few more sheds, doesn't look bad to me at all! Good looking pinstripe though, lots going on with that pattern.