Kafka lost data

Hello folks,
I recently noticed our message amount in kafka seems to have dropped
significantly. I didn't see any exception on my consumer side. Since
producer is not within my control, I am trying to get some guidance on how
I could debug this issue.

Our individual message size recently have increased. Will that cause
message drop if it exceeds "message.max.bytes" on the broker side? If so, I
should see Exceptions on the producer logs, is that right? or is there some
kinda broker log I can check?

Thanks,
Chen