There wasn't any news release I don't think as some changes hadn't been fully rolled out, at least on 1.
On 2, there are a couple of different things happening. One is that there are new backend ratings for puzzles, that are often different than what is shown in the UI. At some point the interface will be updated to show the new ratings. Also, some members have a slightly different puzzle selection algorithm as well. Not sure if either of those will get an announcement when they are fully updated and everyone is back on the same algorithm.
There seems to be recent changes that have been implemented into the puzzles / tactics mode:
1. You can now have coach to essentially tell you what the idea of the puzzle is about - I can totally see why this can benefit (newer) players; but still getting the same (?) rating when solving puzzles when having this option activated seems to completely defeat the purpose of having puzzles rated. (That being said, it somehow defeats the purpose of solving puzzles in general, because having to find the key idea and calculating if it works or not is the main and crucial part of solving a puzzle)
2. Apart from my regular puzzle rating range, I seem to get much lower (like, 1000 rating lower) rated puzzles on a regular basis now, too. I actually somehow like this, because having a wider range of difficulty rating in rated puzzles makes training with puzzles more applicable to real games.
But, is it intended like this?
3. What (else) exactly has been changed? I can´t seem to find any news article on this.
It would be great if the site would inform us as users when such dramatic changes are applied, so we don´t need to figure out on our own.
Thanks!