Difference between "after" and "since"

Hi there, I have a question related to the usage of "Since" and "after". Actually I found these three sentences on news articles. And I have seen a large number results both in "news" and "Ngrams". Are all these sentence using "after" is correct. I think "since" would be the preferred choice here. And my question is, is the third sentence is correct as written?

1- But, while in April, it was suggested that these three seats would be the sole focus of the Scottish Labour campaign, that attitude has changed after the local elections.

2- A 34-stone man mountain who binged on £5,000 of takeaways a year has shared intimate photos of how his body has changed after losing more than 14 stone in just ten months.

3-Prof David Kipping, of New York’s Columbia University, has been using the Kepler Space Telescope to search for moons around other worlds for years, without success.
‘We’ve had candidates in the past and investigated them, and most of them have evaporated,’ he said. But it seems his luck has changed after he and his team spotted larger-than-expected dips in the amount of light visible as a planet passed in front of Sun-sized star Kepler 1625.