small cracks in joint compound JOINTS
Fiber mesh tape was made for rapid-set (chemical dry, not air) compounds- 20 minute, 40, 90. I would have used paper tape with your mud. Green board has been proven unacceptable for use in wet locations. Most, if not all jurisdictions won't allow it there. As you probably know, since you are painting it. You could apply another coat, total of four, to try and hide it.
When you say corner trowel, inside corner? That is some extra work to get it to cover mesh. Try paper in the corner or a pre-creased rigid one, you'll be amazed at the application difference. Be safe, G