I too thought I was imagining it. But when I started sneezing due to the dustiness of it, I knew it was different from previous bags. One of the main reasons I use it is to stop the sneezing! My sister who has some (in London probably purchased from PAHome) also said she had noticed it was finer and dusty too.
It is almost as if it has been stacked too high, and been crushed. Mine came from a well known veterinary product supplier, who up until now, I could thoroughly recommend.