Tissue Necrosis, pests, or something else?

[CCauthers]

I have an a. tenuis frag that I received 1 month ago. It was in very low light, 115 par, and I placed it in my tank an gradually moved it up to 4-500 par in my tank. It has been in its current spot for around a week, and it's PE has been a little lacking. My urchin was wrapped around it yesterday and scraped the base a little, and I looked at it today to make sure it was fine. When I did this, I saw that the underside of the frag has red striations over a white/off-white base color, which is not occurring on any of my other sticks. Pictures are attached below. The frag has been coloring u quite well, from pretty brown to what you see now. My question is: are these striations something I need to worry about? Is it something I can fix, if it's a problem? Thanks all.

 

[CCauthers]

Bump, really worried here

 

[CCauthers]

To update this, this morning half of the flesh is gone, likely will be completely gone in another 6-8 hrs judging from the current timeline. RTN started at about 6 this morning.

 

[Urtoo]

I fragged a Stylo once that had STN from a badly mounted drag above it that fell on it. That little frag grew out well.
I cut it a little higher that the flesh that was dying. A local reefer back then (15years ago) basically said it’s like a venom bite and is killing it underneath, and fragging helped me in that situation. But it was a Stylo, so ymmv

 

[CCauthers]

I fragged a Stylo once that had STN from a badly mounted drag above it that fell on it. That little frag grew out well.
I cut it a little higher that the flesh that was dying. A local reefer back then (15years ago) basically said it’s like a venom bite and is killing it underneath, and fragging helped me in that situation. But it was a Stylo, so ymmv

I've done that as well, but this one rtned from the backside, so there wasn't anything I could cut and I couldn't glue all of it either. I also wasn't there when it started rtn