Pink Monti: Black lines through it

[gmpolan]

So i was looking at my frag rack the other day and noticed a frag of pink monti that i got from Rit has like deep black lines through it. All my other corals are fine except this one. Any idea as to what this could be from? Nudibrach?

 

[gmpolan]

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[snowmansnow]

is the black area dead tissue?

 

[gmpolan]

Thats what it looks like but i am not sure, as i have no other issues with any corals and my params are fine. It has been sitting on the frag and rack and i noticed that the other day..