Lee Anne, I'm having the same problem this year, and I was blaming it on all the rain. What I have noticed, though, is that it's my new hybrid teas that drop petals quickly. The ones that have been in the ground for a few years seem to hold on better. Maybe it's an adjustment problem?
I'm guessing. I don't know. Maybe something got into the bud and chewed so petals came loose?
Still guessing