SLP's - incremental backups are size of full backups while doing to tapes

I implemented SLP's to push my backups on disk to tapes. but surprisingly, my incremental backups are also of equal size to full backups and running into many TB's which is turning as a concern

any suggestions here will help me to reduce on the tape utilizations

here is nbstlutil report o/p 

Backlog of incomplete SLP Copies
        In Process (Storage Lifecycle State: 2):
                Number of copies:       1239
                Total expected size     151536045 MB

SLP Name: (state)                                 Number of copies: Size:
SLP_Daily_NBK02_TLD1 (active)                                911    88910657 MB
SLP_Daily_NBK04_TLD1 (active)                                313    50905427 MB
SLP_Weekly_NBK02_TLD1 (active)                                13     5058928 MB
SLP_Weekly_NBK04_TLD1 (active)                                 2     6661032 MB

Total:                                                      1239   151536044 MB

let me know if any more details required from my end

thank you