Rusted metal thing and marble tile tarnish in bathroom

[Mich]

I'm moving out after 2 years and 7 months of renting period. The condo has master bathroom which we family of 3 used few times a day. The owner is going to charge us for the following: the metal lamp holder attached to the wall is all covered in rust. Air vent (air fan tuned on automatically with light) and towel holder has some minor traces of rust too. Other than that, marble tile in a bath tarnished on the place water comes on. The latter is probably because of temperature differences as I was explained: when we stepped in the bath we usually first pointed flow of cold water to the wall until it warms up in several seconds and then pointed to our body. The shower room has glass doors which makes us hard to reach the faucet, we had to step inside first. So the owner is going to replace this stuff at our charge. She argues she used to live here for 7 years before and it was in good condition all the time, and we did something wrong in less than 3 years. So I wonder what wrong we might did so that she had this metal thing never rusted and marbal tile always in shiny condition? How typical it is for metal holder in bathroom to get covered with rust in 2.5 years? The only explanation I have is we used it much more often, it is 3 of us and we took shower at least in the morning and evening. Would you consider this problems as a result of "normal wear and tear"? Thank you!

[pushkins]

Renters are not usually held responsible for rusting towel holders etc... depending on the quality of the finish many of these will show signs of deterioration at some point of their lifespan, I have seen cheap brass looking rails show rust signs in as little as two years. Also remember that the towel holder is supposed to hold damp towels after you used them, so any argument the landlord uses for replacement due to rust is absurd.
The bathroom fan turning on at the same time as the light pretty well negates any landlord argument about not running the exhaust fan to take out the moist air from the room and I doubt your lease had any mention of requirement for you to have "cool" showers.

It should also be noted that the shower door opening MUST allow access to the shower controls without stepping into the shower, this is a safety issue so that the temperature can be adjusted safely BEFORE entering the shower. This is especially important for rental properties as if a tenant gets hurt there are serious insurance repercussions.