SPS Help exposed skeleton

[Ryan]

I bought this piece about 3 weeks ago at a local retailer and it was doing really well. I noticed this the other day and was wondering what it was? Is this STN? I doesnt seem to be getting any worse than 3 days ago. This patch was about .5" - .75" away from a small mille frag and thought maybe it was from the mille stinging it so I pulled this frag and put it on my rack.