Hera would explain, eventually, what was happening with Harmonia. Once it was more settled, and once her grandchild was more secure in herself. If Ares' daughter thought that her grandmother had been hard on her upon her return, she certainly was not up for dealing with Zeus.
So all she said in response to the look sent her way was, "Harmonia is adjusting after quite some time away. It's a lot to catch up on."
And then he brought up something that she hadn't known. Tilting her head to the side, Hera commented, "No, actually I had not realized. But he's never been one to broadcast his feelings, he's far more subtle than his siblings. You are closer to him than I am, however, and I trust your assessment. Do you think it is something of a... personal... nature?"
As far as Hera knew, there was nothing in his family that should be upsetting. And were it a threat on Olympus, he'd already have told Zeus as was his duty. The boy was a stickler, in many ways. So what was eating at him?