Someone made a suggestion to me that sounds very plausible. The marks appeared the night after his last shed (6 weeks ago). I didn't actually se if they were there already b/c it was dark as i was taking him out, but as i did he got all squirrely on me and tried to go behind some shelves. I had to tug him a bit to get him out, harder than i wanted to, but if he had gotten into this particular spot theres no telling how i would have gotten him out. So then i notice the marks, and it looks a lot like one time when i actually saw him get his head stuck scrape some scales getting out, so i assumed thats what it was. So the suggestion made is that the injured scales from that night 6 weeks ago didn't get to heal completely before he went into his cycle this time and these marks reflect the unhealed state of those scales. The assumption is that they will heal and go back to normal within a couple of sheds. Thats fine with me, i just hope its that simple.