Your send suddenly spikes in bounces. Is it reputation, authentication, an ISP block, or bad data?
Drop your _Bounce export and get a diagnosed incident report that tells you where to start.
_Bounce query (SFMC SQL / Automation Studio)SELECT
b.JobID,
b.SubscriberKey,
b.EventDate,
b.Domain,
b.BounceCategory,
b.BounceType,
b.SMTPCode,
b.SMTPBounceReason,
b.SMTPMessage
FROM _Bounce b
WHERE b.EventDate > DATEADD(DAY, -30, GETDATE())
SELECT Domain, COUNT(*) AS Sent FROM _Sent WHERE EventDate > DATEADD(DAY, -30, GETDATE()) GROUP BY Domain
_Bounce data view; confirm against your account.