Your nem still looks quite far from death in the photos above. My knee jerk reaction is that it is bleached and the discolored tentacles are those that are normal coloration. Given that they appear to be on the underside specifically and in my experience, when they recolor, it tends to be more of an overall change, I am interested in the questions below.
We can offer you more help if we get some stats on the tank.
Size, age, lighting, specs (how much live rock, sand?, and filtration) and tank inhabitants.