If you're improving upon your personal bests then you're obviously improving.
"Have the other players there suddenly become lousy?"
No. You've probably made a psychological step in your game or something else, and something "clicked".
We all go through slumps and high periods, and it's up to us to try to maintain the high period for as long as possible. I have had 2 large slumps, dipping from 1500 to 1300, and 1800-1650. (That's not on RHP, rather Internet servers where I usually play 60 5). Now, I have maintained around 1900-1950 for a while after jumping from 1700.
The high point of your rating is really how good you potentially are, the low point is how had you can become. That is, without changing your playing strength at all! You have to focus on what psychological factors are impacting you and you can pull your rating back up to your all time highs and keep it there until you increase your strength. When I went through my first slump I would play a ton of 15 0 games a day, and at first start winning a little. Then when I lose a few games, I played a lot more to try and regain the rating I lost. Eventually, my rating went downhill.
I began to discipline myself and eventually pulled out of it. In my second rating dip, I was watching TV and listening to music whenver I played and I made big blunders. I changed that too, and now I'm a much better player.
So you must be doing something right as well.