OK whilst enhanced log levels in the jobs logs do cause disk space issues these take place against the DATA folder and NOT the CATALOGS folder.
The catalogs get large because of the amount of individual backed up data items they have to keep track of - the larger the number of files or e-mails being backed up the more entries are contained in the catalogs and the larger they are. Kind of means that the reason your nightly catalogs are now bigger is that you have a lot more files or e-mails being protected.
As such you do have to allow enough space for catalogs and it therfore can mean it is better it install BE on a volume other than C: - or move the catalogs folder to another volume after the install.
BTW catalogs for tape sets are removed when you overwrite the sets, catalogs for DLM sets are removed when reclaims occur, the truncnation setting does a partiel remove of catalog info, however I hope you are not deleting catalog files from the file system as if you are then:
- disk based backup sets will not be reclaimed correctly and you will end up running out of space in those locations instead (or backup data being deleted earlier than intended)
- tape based sets will not show up in restore selections so you would have to keep manual records of when each tape is used and what it contained to know what to get back for future restores.
As an aside BE 15 FP4 introduced a quick catalog option for GRT sets which should use less disk for the GRT catalogs (it makes the backup processing quicker but opening a restore selection list slightly longer)