Hmmm, not sure about this, but I wonder if it is going to split. I recall reading a thread several years ago where a new BTA split a few days after going into a guy's tank. It wasn't a large BTA and the guy who posted the thread suspected the stress from the move caused the split. I followed that thread for a while and both 'clones' did well. My BTA has never split, so I don't have any first hand experience, but I kind of remember that in the pre-split photo the guy showed of his new nem it had a mouth that kind of looked like yours. I am sure others who have had nems split could say if that is what they look like (I suspect there are a few photo logs of splitting BTA's on this forum somewhere).
From my little experience, all I can suggest is to maintain the great water parameters you have, leave the nem alone and hope for the best. It is a beautiful color, by the way.
Good luck,
Kurt