New FireCuda 2TB Transfer Rate Is Slower Than The Older 1 TB

Hi I have brought a new Seagate FireCuda 2TB SSHD to replace an older FireCuda 1TB SSHD as well , I still have both running the windows 10 system , I happened to realize that on copying files to external hdd through USB 3 average transfer rate of large files is 50 mb/s from the 2TB drive and 75 mb/s on the 1TB , there is no particular difference between both , I even managed to defrag the 2TB drive but still I get an average 50 mb/s as if it was capped or so , the only spotable difference between the 2 drives is that the older drive is thicker where I believe it has 2 metal discs inside unlike the new 1 TB slim disk that is almost half its size , would this be the reason to drop the performance by 50% ? or is it something I am missing ?

Is it a 2.5" SSHD? Because the 2.5" Firecuda have 5400 RPM and the 3.5" have 7200 RPM.

its a laptop 2.5" 5400 RPM both , sorry i neglected to mention .

well my own benchmark was transferring same video files to same WD USB 3 drive twice just to make sure , they were 2 files of 10 GB and 20 GBs respectively , 1 TB did it in 75 mb/s and 2 TB did it in 50 mb/s , i doubt there are any problems as both disks are from same manufacturer from same model and yet the new one performance is hindered , but if CrystalDiskMark detect and fix them ? and what to look for in its results ?

Crystal disk is used to benchmark your disks and read the SMART status on them located in firmware. If you can run it on both your firecudas with relatively same sequental cycles, and the SMART screen are similar aswell, then that would be the goal.