Iron out is a little citric acid and some chemicals to reduce the iron to make it soluble.
You can also just add citric acid, (2T/40lb bag of salt) or buy the iron defense type softener salt that has the acid and detergent in it.
https://www.lowes.com/pd/Morton-40-lb-Salt-Pellets-with-Iron-Reduction/3332700
When I bought my current water softener, I was told that having iron in my water, I should expect to change the resin in the water softener every 5-10 years as not all of the iron that precipitates on the water softener resin comes off during the salt regeneration. We are in that range now, and I am not seeing any degradation of the softener performance, yet. YMMV.
All the best,
Peter