How to tell a manual action from an algorithmic drop
Traffic falls for many reasons and most of them are not penalties. The distinguishing test is simple: open Search Console's Manual actions report. If it is empty, no human has acted against the site, and the cause is an algorithmic change, a technical fault, or seasonality.
A manual action names the violation and its scope — site-wide or specific URLs — which is more diagnostic information than any algorithmic drop provides.
Recovery is fix completely, then request reconsideration with a description of what was wrong, what changed, and what prevents recurrence. Partial cleanups are routinely rejected, and each rejected request costs weeks. It is worth over-fixing before submitting.