Does my torch still have a chance?

[marcingo]

On boxing day I bought two torch frags one had neon green tentacles with bluish tips while the other had reddish tentacles with green tips. The problem I am having is with the neon green tentacles torch. All other corals in my tank are doing fine. All my levels are at zero except nitrates are at 20. Now to the problem. The torch with the neon green tentacles seems to be losing tentacles every night, when I wake up in the morning there are less and less tentacles except the wierd part is I dont think they are falling out since there is none on the sand bed. This morning I woke up to find this torch had lost all its tentacles and all thats left is a skeleton. But again they are nowhere to be found could they have just retracted into the skeleton? Also what could be causing this (just a bad frag?) I dont think it should be water quality since the other torch seems to be doing great both were placed on the sandbed on opposite sides of the tank. Midway through the week when I saw the one torch was having troubles I moved it onto the rock a little closer to my lights to see if that would help. Any ideas anyone? By the way I have a 17 inch tall tank with 2 175 watt MH HQI bulbs one which is a 14k and a 20k. I am now doing a water change to get the nitrates to zero and to see if maybe this may help the one torch- If all the tentacles are gone does that mean the torch is dead and I might as well throw out the frag or does it have a chance for a come back? Again every morning I looked I never found even one tiny tentacle on the sandbed or the rocks (last night it lost quite a few tentacles and again none anywhere to be found) If something is eating it wouldnt it go after the other torch too?

Thanks