Is the custom valid which stipulates that the second wife does not inherit from properties that came into existence during the period of the first marriage, and that both wives inherit from what was added to the properties during the period of the second marriage, and are there other solutions for the issue of the second wife's inheritance?

Allah permitted a man to marry more than one wife, up to four. If a man dies and has more than one wife, they all share in the inheritance without discrimination, according to the Almighty's saying: "And for them is one fourth of what you leave if you have no child; but if you have a child, then for them is an eighth of what you leave." Believers must submit to Allah's rulings and not object to them, for that is a great danger. Properties belonging to the wife through gift or Mahr are not included in the husband's estate, while whatever the husband owned until his death is included in his estate and distributed among the heirs. The husband must be just among his wives in gifts and expenditures, and it is not permissible for him to favor one of them with something over another except with her consent.