The good news is, this actually sounds pretty normal. 24 hours to reflect changes in content is better than many sites. I can't account for why it dropped from 4 to 24, but I'd say this is still in the range of "good"

There are a few possible reasons Google might adjust rankings after seeing a change in your title and meta descriptions. Among them: (keep in mind these are only possibilities)

1. The algorithm determines that the page is less relevant to the target query keywords

2. The title change deviates from earlier anchor text pointing at the page, meaning the page might not be as relevant to the query

3. Over-optimization

4. After changing your title+description, you experience a lower CTR in search results. In theory this could lower your rankings. But because you describe the old title/description still showing in SERPS, this is less likely

5. The drop in rankings is temporary, or is unrelated to any changes you made.

If Google is still showing the old title/description, #5 is a strong possibility. You may want to check Google's cache of the page to see if it's picking up on the changes. Depending on the site this can take anywhere from a few hours to several weeks.

If nothing else, you can always change the title/description back to the original version and test what happens.

Great question! We do often see a positive correlation between the number of followed outbound links and higher rankings (though I'm not sure we've scientifically measured this recently). Anecdotally, we hear this often as well. Most famously when the NYTimes made external links "followed" which was followed by an increase in traffic/rankings.