[Hondaracer]

What you could do is cut out some of the drywall a few inches off the corner to have a look. Keep the hole below the baseboard line. That way you won’t need to have any major drywall repair and baseboard will just cover the hole you cut

Imo it doesn’t really look like it’s been consistently wet but it’s kind of hard to tell. The tack strip does look like it has been wet before though