Why am I getting worse?

I’ve started playing ACC maybe 2 or 3 months ago and I’ve got around 100hrs in the game. I’d like to think I’ve seen decent progress since I started playing despite still being amateur level, but more recently (last 1-2 weeks) I’ve noticed that I’ve actually been getting worse. And I’m not talking about slightly worse, but like MUCH worse. All of a sudden I’m almost a full second slower on my favourite track (spa), Additionally, I’m consistently almost 2 seconds slower on brands hatch which I haven’t raced for only 2 or 3 weeks. What should I do to try to improve again?