Nick, I tread very lightly here because it's dangerous to read the complaints of an aggrieved spouse and make conclusions about exactly what's going on.
That being said, what you describe throws up a few red flags. The good news is, there is very successful treatment if in fact, PPD is what you are dealing with.
I think it will be helpful for you to look into your W's situation in a more in-depth way. You might want to make an appt for you with an IC who works with these issues to discuss things. I don't know where you live but look for resources for postpartum depression/perinatal mood disorders. Research postpartum support international.
There is a great book, Postpartum Husband, which could be very helpful.
Don't talk to her about this until you are sure you are on the right path and know exactly how you want to proceed, hopefully with the guidance of a skilled therapist. She probably thinks she's just fine or at least is trying to appear to be just fine.
PPD can be very scary for the woman as well as her family because she often does turn into someone you don't know, someone she doesn't know.
Take care of yourself and your kids. Love your W.
Me 57/H 58 M36 S 2.5yrs R 12/13
Let me give up the need to know why things happen as they do. I will never know and constant wondering is constant suffering. Caroline Myss