I see you are in Wash. State. what part? I lived in Vancouver for about 5 years Did a lot of inspection up that way. very odd soil condition from one thing likes Rocks every where to full on standing water under home with very high water tables and just flat out mud...

Basements up that way are just a pit for water to collect.
like any dam they leak...

I have only ran into one basement that had no water stains in it in all my years. I think Raymond has a hand on it you did the right thing by going back...

Are there any exterior drains to help divert the water from the exterior of the home? that helps in a big... Before I would say do anything on the interior of the flooring or walls. get working on some exterior drains and they may need to be 5 to 8feet deep to help.

Best

Ron