I bought this brugmansia last year, and I’ve called the grower and spoken to the greenhouse where it was bought and niether had a clue. Started with leaf discolouration, deformation, curling, and all big leaves dropping. Stippling and strangeness with tissue death at leaf edge. Took a ‘scope to it, no bugs, and no signs of root rot. Fertilizing with gypsum, liquid kelp and increased watering saw reduced leaf deformation, bigger leaves, no edge necrosis. Now these spots are coming in over the dark green colour on some leaves. Humidity 35%, partial sun, cuttings also show mild discolouration but no spots, any ideas?
That was kind of you to post the follow up even though no-one here was able to help. At least we can help the next person who asks. The excess nitrogen was in the soil it came in, or in a fertilizer you were using?