If you know information on either person in the shidduch and that is bothering you and you want to know whether to say something or not, you need to discuss it with your own Rav. Some things must be told and some things not. In addition, what you might think is so important might not be seen as a very important issue by a learned Rav experienced in shidduchim or life in general. If that is what this is all about, speak to your Rav and be satisfied with his answer. You have done your job by bringing it to the attention of a Rav who knows the halachas involved. Do not say who the people involved are or that may sway the decision just why you feel it is necessary to share the information and ask the sheilah.
If you are talking about your own shidduch then speak to your own Rav or Rosh Yeshiva with your concerns or speak to the known “Chassan Rebbe” of the yeshiva who can help you sort out your thoughts and feelings. You can also seek the counsel of a dating coach.