Arrey Balaji, no ji.... 2ji much hogayaji.
Hi you can call me mukesh.
Good to no that no issues in rear drum brakes.
I feel that removal and refit of brake pads is what the service centre may do.
Have a joint test drive with the SA. And let him acknowledge the issue.
Then stay with the vehicle and keep observing.
It's brake dust that has smeared with water.
This will stop when the new brake pad wears out gradually.
For heavens sake don't pour bucket of water on discs, as they may temporarily make the brakes less effective.
If at all to get maximum from brakes in wet condition, one has to brake-release, brake- release the brakes. ( Keeping in mind no vehicles at the rear).