White precipitate on A.nana.

It looks like one of my A.nana has a white precipitate on it. I thought I read somewhere this was an indication of an overdose of a nutrient but I can't find info on it (maybe it was a bad dream )

I have seen pics of A.nana with white spots, apparently a natural coloration. Maybe this is it?

Not really...maybe...could it be an N deficiency? It does look like the second set of pics. I test/dose NO3 to keep around 5ppm. Could the stem plants be depriving the slow grower from N? Hmmm, maybe I should keep NO3 around 10ppm?