u/Enough_Shoulder_7049

Moving into a rental soon and all the windows have a little bit of this. In the caulking (able to scrape clean off).
The owners moved out in December and had lived there the past 12 years with their three kids and no complaints. Then previous it was the owners parents home. I also have a bit of a musty smell issue coming from the master bedroom and cannot for the life of me figure it out. House has been sitting vacant since December and have not found any mold growth on the walls, under sinks, etc. wondering if the smell could be coming from dry drain (drain is gross) in the bathroom in said bedroom.
How do I clean these windows? Is this concerning?