Why would you want to know these things about your Ex?! Nothing good can come out of it. You're (like you are now) just going to end up with hurt feelings. And, now you're upset with your daughters. Stop. Don't dig up the past.
A long time ago, my parents divorced and both remarried. I kept the 2 completely separate. My relationship with my father, as well as his wife didn't have any impact on how I felt about my mother. And vice versa.
Please, just work on your relationship with your daughters and don't ask about the Ex, the GF, etc. Don't expect them to share that with you. In fact, ask that they don't.