We just moved into a newly flipped house, and one thing we've noticed in the showers are that the vertical corners are filled with grout, and then covered by caulk. I've always been told that any tile joints that change planes should be caulk, not grout, so that the grout won't crack as things shift over time.
I was able to notice because the caulk doesn't cover the grout very well, so I probably should fix that regardless. Can I just put a new layer of caulk over what is already there, or do I need to remove the previous layer first? Do I also need to remove the grout and replace the whole joint with caulk?
To address some questions in comments: The whole bathroom is less than 6 months old, so it's all in good condition at this point. I ask my question because I understand this to be bad practice and so it should be fixed to prevent issues in the future (mold, cracks, leaks, etc). If people don't think this is a problem then I'm happy to leave it as-is.
Here's a close-up of the worst section. The grout is about 0.25" wide.