With the LR being broken down and being porous it just makes sense to me that hidden/stagnant/anaerobic areas may have concentrations of chemicals being released that would otherwise be diluted and removed via our various export mechanisms. I have no scientific data to back me up... just MYHO.
There was mention earlier of a lot of changes happening in Jason's tank over a short period of time;
I haven't been following his tank history, but I did come across an article that indicates that changes in a coral's environment can actually turn the coral against itself.
Here is the article:
http://oregonstate.edu/ua/ncs/archiv...se-coral-reefs
Mitch