There are many sources of stress and strain for them all converging at once (in no particular order): new baby (who knows how much sleep they are getting - easy to assume they have night nanny but perhaps not), newish relationship (let alone marriage), baggage on both sides from family histories (common for stuff to resurface with big life events/changes), unresolved grief perhaps for Harry (more common with traumatic deaths or deaths under unusual circumstances)... Then add to all that, sudden, intense public scrutiny that she in particular may have been finding overwhelming... He is terrified that she will say she's had enough... Didn't William talk candidly ages ago about how important it was to find a wife who could hack it all and how he took a long time in finding out or trusting that Kate could indeed do that? Harry is maybe facing that question now (which must be a difficult one to handle) BUT having already married and had a child. Then linking in and muddled in with all of it is his grief etc around his mother and her unhappiness and death all bound up with press intrusion, and gosh, my own head hurts just thinking about it.
He and William believe in combating stigma around mental health - maybe Harry (wisely or unwisely, who knows?) has decided that he will practise what he preaches and be more open. He seems desperate - maybe he thinks that if he appeals to the public and press in this way it will all go away. I can easily see how he and Meghan forging their own path, not in the model of William and Kate, would cause tensions.
Interesting that the headline tonight is that William has expressed concern about Harry. Seems strange... PR to show that he still cares about him and aim to play down the idea of a rift? Makes them look almost estranged, William communicating that he cares to him via the media.
All does seem a bit tense. I feel sad for them. Human suffering of any kind - anxiety, anger, sadness - feels difficult regardless of how much money / status etc one has, although of course their access to sources of support etc are likely to be greater.