WD Black 1TB running slower than specs

Hi, today I’ve bought a WD Blue 1TB and decided to run benchmarks on both it and my old WD Black to see how they compare.
I got wildly different results in favor of Blue.
This seemed a bit odd, so I checked the specs and it says that it should be around 150 MB/s, but I only got around 60 on Black. My harddrives are divided into 2 partitions and interestingly enough, one of the 2 partitions gets better read speed results than the other (for WD Black. And I do realize that data on the outside can be read faster than the data closer to the center but unsure by how much faster).So I ran the test for all the partitions and this is what it looked like.

2 on the left is Blue and 2 on the right is Black.
SMART shows that the drive is good and the quick test has passed with no issues (using WD’s diagnostic tool)
What is the reason for this slowdown and is it normal for it to be this below spec?

Extra info:
WD1002FAEX-00Y9A0 WD Black (Note that the drive was bought in 2013 in August, so it’s almost 5 yo)
WD10EZES-08WN4A0 WD Blue (Running inside an external USB3.0 enclosure, and using GPT instead of MBR)
Asus H81M-D motherboard
Intel i3 4150
How the partitions are organized:


A hard drive speed depends on various factors such as:

1)Read/write speed
2)Booting Speed
3) Seek Time
4) Recalibration time
5) Head Issue

And to measure the exact issue, you have to share the smart report of the hard drive. You can download the hard drive smart report with the help of HARD DRIVE SENTINEL TOOL. Hard DRIVE Sentinel is a multi-OS SSD and HDD monitoring and analysis software. Its goal is to find, test, diagnose and repair hard disk drive problems, report and display SSD and HDD health, performance degradation and failures.