You can never treat your wives in an equal manner, even if you do your best. But this does not mean that you can leave a wife of yours in limbo (not having a real marital relationship with her nor divorcing her so that she may find a better relationship.) It will be ideal to establish a peaceful marital relationship in order to please the Lord as God [will take it into consideration and you will find that the Lord] is Merciful and Forgiving.