Yeah, some cultivars are more susceptible to these "growths" than others, but it's never normal unless it happens all of the time. It's certainly nothing to worry about. Sometimes stamens morph into petals (petaloids) or as in this case,
try to morph. Often these petaloids are how double flowers are achieved. Or, sometimes extra petals just "grow". The cause for these one time anomalies is usually some fluke environmental trigger (many possibilities), and seldom repeats, except in susceptible cultivars.
One of my own martagon section hybrids had one of its flowers with nine petals this year. It's interesting because I have two siblings with similar genetics that both "malfunctioned" at exactly the same time. Sometimes these oddities can look nice, but usually they just look weird.
