I'm attaching some pictures I took. This has been an ongoing problem with the baseboard pulling away and fine black dust left where it pulls away. There is a crack under the window that has gotten bigger. This occurs all along this short window under a set of three windows. The paint which is not new (painted 4 years ago) has started to bubble as well. I want to know if it's a major problem or traditional settling. Our house was built in 1999.
There are a variety of reasons that this could happen from humidity levels in the home to cheap paint to mixing a primer with an improper top coat.
However... what you are describing sounds like your windows are leaking. I think that water is penetrating under your windows. The crack is probably due to water sitting in the framing causing it to swell until it dries (if it does).
I would pop that whole run of baseboard off and take some pictures for us. The paint on the baseboards plus the baseboards cracking where it meets wall plus the other stuff going on makes me think you will find mold behind or the start of mold.
From there we need to fix the root cause which might just be some caulking or an inherent issue with the window and you may need to redo a little drywall on the interior. But I doubt this is just a paint issue.