Hamlet, deeply grieving his father's death, has chosen to wear mourning clothes which are seen as excessive and inappropriate by the court.
Here's a breakdown of their concerns:
* Claudius: He sees Hamlet's mourning as unnecessary and disruptive to the court's decorum. He wants Hamlet to move on and embrace the new order he has established, including his marriage to Gertrude.
* Gertrude: While she shares Claudius's concern about Hamlet's mourning, she is also worried about her son's mental state. She is concerned about his melancholy and worries that he is losing his mind.
Both of them are concerned about Hamlet's unconventional behavior, which is a reflection of his inner turmoil and rejection of the new reality. Their concern highlights the societal expectations of grief and the pressure Hamlet feels to conform.