IME, the flowers are very susceptible to the vagaries of the weather - mine got hammered this year from the windy rainy week, then the ungodly hot week; it was clearly not a combination they liked as they, like yours, fell apart quickly. They aren't long-lasting flowers at best, not like a columbine's flower is, but they usually last longer than they did this year. So, chalk it up to the weather and wait for next year (also known as the Cry of the Gardener).