The niger seems to be continuing to recover. Got him to feed this morning, first started picking at some of the debris from the pinktails food and then took a large piece of shrimp tail on the end of a stick.
The pinktail started showing the first aggression I have seen between the two, trying to chase the niger away from his stack of rocks (they were both in this part of the tank this morning and are back in it now after feeding), trigger up and a few tail swipes and charges towards him, plenty of grunting. The niger for his part seemed that he could not have cared less about this treatment, swimming around the tank a couple of times before returning to hide in the stack the pinktail was trying to oust him from. The nigers trigger is fine but the first few spans of his dorsal fin from the trigger are nearly non existant, seems to have simply worn it off rather than being bitten though. No visible signs of ich anywhere on either trigger, I know sometimes that this doesn't show, but, nothing has suggested it to me either by behavior or appearance.
I think the niger seems to be recovering nicely, more active, not panting, feeding properly, there seems to be a fresh membrane growing at the tips of his anal and dorsal and tail fins and there is less raggedness towards the ends. There is another set of hiding spaces on the right hand side of the tank if either is evicted from the left.
johnnybravo - I think you are right and I think the basic cause of this is me stressing them both out moving the rocks around shortly after they were put in. I should have simply left them on their own for a while longer (2-3 days rather than a half a day before moving stuff/shoving food in their faces) and given them time to adjust.