I’m sorry to hear that you are having problems with your WD drives. Even though the firmware version might vary, as long as the model number is the same between hard drives, the performance should be the same. Check the link below so you can test your hard drives using our DLG utility.
How to test a drive for problems using Data Lifeguard Diagnostics for Windows
If the DLG test you may create the RMA replacement number following the instructions from the following link.
How to get an RMA, (Return Merchandise Authorization) or replace a defective product under warranty