As an amateur weightlifter and professional programmer, I've definitely noticed reduced performance following a hard release cycle.

What's interesting is that I usually hit PRs immediately after a mental fatigue, but a week or so afterwards it catches up with me and my performance in the wightlifting hall goes down.

I also lift. You're not going to be able to maintain the peak required for PRs week over week. Don't even try. Take the gains as they come, focus on your training, diet and sleep.

If you feel like you're not improving, change something.

Weightlifting is mostly mental discipline, acquired via training. A very large percentage of the increased weight you can move is due to improved form and increased recruitment of the existing muscle tissue. (This is why newcomer gains are so large.)

> If you feel like you're not improving, change something.

Just make sure you give it enough time to make sure it's truly a plateau (measured in weeks or months depending on how long you've been training). Bouncing around to a new barbell program every 2 weeks will do you little to no good.