I know of a case where a Rosh Yeshiva proposed a Shidduch between a Talmid and a frum girl whose father was niftar. 2 children later , the chosson decided he did’t want to be frum anymore. The girl’s mother called the Rosh Yeshiva and said, “how can you do this to me.”
The Rosh Yeshiva answered, “We thought that when he got married, he’d straighten out.”
Bottom line, take what anyone says with a grain of salt and use your own judgement and instincts. If you know a of serious problem that could affect the person’s life, you should tell. Ask a Shaila of a Rov who isn’t nogeah b’dovor. When in doubt, don’t speak irrelevant Loshon Horoh, but you should look at it as if it were your child.