I don’t know about the Iron or the Potassium but I looked in my Adelle Davis books and she did recommend the calcium for the strontium.
It is more important if you are low on your calcium intake, than if you don’t have a deficiency. Another of my books also recommended apples for their pectin. Not sure about that, but it wouldn’t hurt and be good for you either way.
I think the main principle is that these radiation related elements are picked up by your body IF you are deficient in the element that is like them. Like iodine for the thyroid instead of the radioactive element iodine.
Hope this helps.
When I was in elementary school, nobody had ever heard of Strontium 90 - by the time I went to college, everyone in the world had it in their bones... Not a good omen...