Hi,
The bloom cycle on these is long, each bloom will last for quite a long time, and you will notice the difference in the first-opened blooms to the newest; the older the bloom gets the more it changes color.
I have some that start white and when they are complete they are yellow.
Don't fret if you walk up and cannot smell them. These flowers only put off the fragrance as the sun sets, this way they can attract the most moths and bats which are the pollinators that are needed. Most bees ignore them.
The seeds, if they form, grow very easily and the little plants can reach full height in one growing season. The Brugmansia seed is in a pod that forms, and the seeds themselves look like pieces of cork material. Don't do the float test on Brug seeds because they all float, just like corks. Nothing to do but pop them into moist warm soil.
Ron