Never sketch a flower one day and expect to paint it several days later - it won't be there. The day I sketched this iris in pencil, there was one bloom on the stem, and there were 3 buds waiting to bloom. When I returned to paint my sketch, at least there was still a flower blooming - but all the buds were gone. I was lucky that I didn't wait any longer!
I'm wishing now that I had erased a couple of the buds before I started painting, but I didn't, so it is what it is.