Exceptional deferred delete speed

We have 4 cores, all running 6.7 and repo size of 200TB plus. 2 cores are primary and other 2 are replication cores +  they do some direct backups. For the most part all cores are performing at the same level. But one of the main backup cores running exceptionally fast. It does deferred deletes between 300mbps  to 500mpbs, while all other does at maximum speed of 150mpbs. Rolls on this fast machines goes way faster than the rest of 3 cores. All 4 cores are running on Dell servers and specs match exactly. All configurations match 100%. Multiple engineers from my team have checked these configurations. Quest support has done the same, but not able to take 3 cores to perform at the same level as fast one.

I have spent months with quest support. Given them mountains of logs and their response was that other cores have white space / fragmentation within repo and they don't have a tool to fix.

Wondering if anyone else know, what I'm missing that could help me achieve same performance on all cores?