How to save an SPS?

A while back I picked up some corals from reefninja before he had to ship out. He gave me an acropora which has not done well in my tank which is mostly softies and has nitrates around 15 ppm. It looked like it it was pretty well toast, but now I see on one branch a new growth has started. Would it be best to snip off this branch and start over, as I don't think the rest of the coral is going to come back.
Thanks!

 

I've set up a rDSB a few weeks ago to see if I could get nitrates under control. It should start to kick in pretty soon. I was also thinking of doing a biggish water change to give some relief. I run chaeto in my fuge, so we'll see if it starts to come down.