RMAN Active Clone And Corruption

I am cloning my prod db to test with the rman active clone command. I can successfully clone my DB, but after a few hours or so I see messages in the alert log that I have corrupted blocks in several datafiles. Note, i dont see these messages in my PROD DB therefore I think that DB has no corruption. I have few questions:

1) I was reading tha having tables or indexes set with the NOLOGGING option can cause objects to be unrecoverable. Would this affect my active clone?

2) I know you can either change a DB or tablespace to force logging. Is there a query I can use to determine if the DB is in force logging mode.

ALTER TABLESPACE tablespace_name FORCE LOGGING;
ALTER DATABASE FORCE LOGGING;

3) Lastly how to check as why my clone DB would have corrupted blocks.

Here is the clone command I am using.

rman catalog=rman/rman@proddb target=sys/sys@proddb << EOT
connect auxiliary sys/sys@clonedb
duplicate target database to clonedb from active database nofilenamecheck
pfile=/u01/app/oracle/product/11g/dbs/initclonedb.ora ;
exit
EOT