Is the wife considered to be falling short in her daughters' rights if she remains silent about demanding that her husband register the apartment in his name, especially since the apartment was built with the husband's money, but the land is in the name of his elder brother?

You are not remiss in your duty to your daughters by remaining silent about urging your husband to register his property in his name. As long as you have advised your husband, you have fulfilled your obligation. However, there is no harm in reiterating the advice or involving some righteous individuals to explain to him that documenting properties and having them witnessed is more protective of rights and prevents disputes.