My neighbor and I live in double wides - they have electric HW heaters
and all piping is plastic. Both heaters are not the originals as we
had to replace them some time back.

He drained his heater the other day and got a lot of rust. Neither of
us have any idea wherefrom the rust is coming.

In any case, that night I noticed my bathtub water was very cloudy,
although the water had not been used yet. The next AM, I filled a
wash basin with hot water, and it was cloudy too. Then I filled the
adjacent basin with cold water, and it was as clear as could be.

So, I am wondering what is happening here. Is it anything I should
worry about? Is the heater causing this somehow? How?

Thanks

Duke