Test the drives with WD diagnostic software (downloadable). If there's any errors, you can check if the drives are still in warranty by entering the serial number here:
WD Support / Warranty Services / Warranty Services for End User Customers
I've had several drives replaced (WD, Seagate) over the years, so it's definitely worth checking.
If they are out of warranty and have errors - you're out of luck.
Sd