Is this shell rot?

[MantisShrimpMan]

I noticed some strange spots beginning to develop on my box crabs carapace. What’s worth noting is that that particular part of his shell spends the most time under a layer of sand, whereas the top region near his eyes tends to stick out a little when he’s buried. I know shell rot is believed to be impacted by light so I’d consider it odd that he was getting shell rot there first.

 

[Ron Reefman]

I've never heard of, or ever seen 'shell rot' in 25 years in the hobby or 20 years of snorkeling.