Following up on my earlier panic thread — I recovered, and I want to close the loop for anyone who finds this later while googling 'traffic dropped 30%'.
The drop: ~30% organic loss, concentrated (thanks to the Pages comparison in Search Console) in one blog topic cluster of three posts. Diagnosed as a quality re-evaluation, not a technical fault — my /full-site-audit score was a healthy 78 the whole time.
The fix: I didn't touch the rest of the site. I rewrote those three posts to be genuinely more thorough than the competitor who'd overtaken me — added original data, updated everything stale, restructured for clarity, and answered the actual questions people had. Merged one near-duplicate in while I was at it.
The result: rankings for that cluster climbed back over about six weeks. I'm now slightly above where I started because the refreshed posts are legitimately better than they were.
Lesson: resist the urge to change everything when traffic drops. Diagnose what dropped, fix that, leave the rest alone.