Here is a good site with troubleshooting and repair info.
http://www.applianceaid.com/dish.html

I doubt that the racks would be adding enough iron to the water to cause a problem but you never know. I would rate that a long shot.

For your racks check out #18.
Note I would just get the touch up, the little repair tips often come off and can cause other problems.

For filming check out #28.
Check your water temp (it should be 120 degrees minimum) and heater itself.
Sometimes a different detergent can solve this. In my opinion, granulated detergent is still the best in spite of the marketing hype.
Sometimes you just have to run a cycle with vinegar on a regular basis.
I like to add it during the longest wash cycle, let it wash for a couple minutes and then stop the wash and let it sit for an hour or so before completing the cycle.
Once there is a calcium/deposit build up you may have to run a number of vinegar cycles to clean the unit.