How refreshing and beautiful!!! This is what I'm talking about with regard to letting watercolor "happen" and be loose! Please photograph your process next time for us.
Working from a B & W photo is a great idea - it obviously freed you up. Your sunlight and value changes are great. Love the charged color in the sunlit and shadow areas.
But moreso, the texture and mingling of pigment, especially in the lower petals where there's interplay from the background colors, is masterful! I love the excitement of the shadow and light playing on the stamen.
The only thing I'd change is to reduce the backround activity near the end of the stamen. The intensity and detail of several pigments there detract somewhat from the hibiscus, which should deserve all of the glory. Maybe a neutralizing wash?
Otherwise, this is sublime! You've handled all of the elements expertly!