Rusty toilet tank and rusty water in toilet

One of my toilet tanks is all rusty inside and the water in the bowl is rusty, and the other toilet in the same house is not rusty in the tank and the water in the bowl is not rusty. What parts need changing in the rusty tank, if any? What could cause this, since it is apparently not rusty water from the house supply.

Thank you.

It may be the tank to bowl bolts.

Replace with brass bolts.