Backup exec 2012 for domino dbs large differtnail

Hi:

I backed diffiental of fullbackup ( aroun 500g) but verynight the lotus db differential is around 300G any idea why such big ..there are some lotsu format of ods 43 most are 51 ....( but they are all native 8 format as i checked by IBM)

http://www-10.lotus.com/ldd/dominowiki.nsf/dx/database-ods-version-should-be-upgraded-to-the-latest-

But here it say it may affect and treat as  changed db always

http://www.symantec.com/business/support/index?page=content&id=TECH76382

is that non 48 will make the software treat it as changed id so daily backup ? if i choose incremental backup will it faster .??? if ods is the issue the incremetanl backup mehtod wouldnt not help right?