“A caregivers journal, with accounts of her experience, gets in the hand of a young person revealing many hidden secrets.”

The second attempt at the logline is better.
It is written from the perspective of the lead character/couple.

You might want to add stakes to your logline, but only if it can be said in a word or two.
---
One more thing.
I like putting what sets the story in motion as high as possible in the logline, although that is a matter of taste. For instance:

When they unearth a forgotten journal, a young couple grappling with the aftermath of war and newfound responsibilities...
---
Good luck with this!

Which war?

This is great food for thought and you are right. I’m leaning toward this. Does it work?

"A young couple, grappling with the aftermath of war and newfound responsibilities, unearth a forgotten journal, prompting them to rediscover the love that initially brought them together and protect their marriage from looming challenges."