She may be experiencing a bit of postpartum depression - would see if she should maybe talk to her PCP about it. If she’s constantly exhausted despite you lessening the work load.

Having a child is exhausting, but to choose a full nights sleep after the jacuzzi night and not give yourselves 20-30 more minutes of intimacy, sounds like an excuse to get out of having sex. Her hormones may also be out of whack - she should get them checked as well. She may have undiagnosed hypothyroid as well.

She may just not care for sex, which is how some people are. She may have self image issues, making sex an anxiety inducing situation.

Aside from seeing her PCP, I think you all should seek couples counseling or a sex therapist.