I remodeled my bathroom less than 3 years ago. Within the last month the water runs out rusty from the overhead shower and the faucet for the tub. It causes the white tiles to build up a rust-like coating. All the pipes were new (I thought). This does not happen in any other room and even in the bathroom, it only happens in the tub area, not the double sinks, the toilet, etc. What do I do to fix this? Is the original contractor or his plumber responsible?

Does this occur from the shower head only? Do you have an access panel on the other side of the wall where the tub valve is?

Yes from the shower head only. I know there is a panel but I would have to break through a wall from the hallway to get to it.

Yes from the shower head only. I know there is a panel but I would have to break through a wall from the hallway to get to it.

If rust is from shower head the only the only logical explanation is that you have an old galvanized pipe from the shower valve to the shower head. Depending on what renovations that were done that may not have been replaced.
If you have an access panel you can see it from there. If not you will have to make a small hole in the opposite side of the wall to inspect. You could also make a small hole in the wall below the shower head and above the tile, if the tile does not extend all the way to the shower head

Thank you so much for your responses! I really appreciate your time and help. My entire old bathroom was gutted to the studs. I don't think an old pipe was used as the plumbing was switched from one side of the room to the other but don't know for sure. If it is a galvanized pipe, what needs to be done to solve the problem? I don't even know what a galvanized pipe is! Would you suggest I call the original contractor or plumber?

Yes, the contractor may to better advise you. Galvanized pipe is iron pipe with a galvanized coating. It last many hears but does rust and corrode. That however takes many years. If all walls were taken down to the studs no one would have left old galvanized pipe piping in or reused it. It is much harder to work with than copper.
You may have old rusting galvanized pipe somewhere else in you water system that is putting rust in the water but you may only see it in the shower.