White and Black spots appearing on Spanish Ribbed newt

[Fane247]

A white spot has appeared on the end of the nose of one of my Spanish Ribbed newts. I looks almost like its caused by a bite from his tank mate. he's also got a dark black spot on the back of his neck. The other Spanish ribbed newt in the tank doesn't have these markings. Is this something I should be worried about?

 

[Fane247]

Is there anyone who can help with this? He's been eating less and less recently and I'm afraid he might not make it.

 

[Fane247]

Also, I've done tested the water with a master test kit. The only thing that was a worry was the nitrate levels which was 40 ppm, which is on the edge of being too much. Not sure if this is having an impact on him or not.