The worst is not having any idea what is causing this. It could be any number of things. She could be sick, or her diaper rash is bothering her, or she is teething, or she's growing, or her temperament is just changing. No clue. OR she could be really hungry, or really tired, and I'm not getting to these needs quickly enough.
I'm going to try to get Steven to journal (God help us) how she does during the day (and also make sure she is sticking to somewhat of a routine.