M.K.
Just a thought (and I don't know how to 'fix' it) but maybe they don't talk to you about their problems because they worry how you will take it. By this I mean maybe they don't complain about how hard it is to do stuff at home or how awful their husband is because they worry about you thinking 'I'm a single mom with no husband, what right do you have to complain?"
I in no way think you think that but maybe it's something that crossed thier minds.
You could just (in a joking tone) say something like, "I'm tired of talking about my problems. You're all married, so I KNOW you have issues you need to talk about. SPILL!!!!"