Well, it seems to me that your soil did pretty good as far as available minerals. It'd also be interesting to know how the soil in each bed tests after you amend them with the different products.
The concentrations of elements in my soil was actually comparable to the rock dust amendments so unless there is some trace element that I missed (quite possible) I'm guessing not alot of difference would or could be seen. Think of it like this. It's like adding a teaspoon of table salt to a bucket of seasalt. It's mostly the same thing in a comparable concentration.
I could see the usefulness of mineral amendments in a depeted soil like a desert or an intensively farmed soil. But a casual gardener's soil with regular compost may be like an unlikely candidate for depletion.
I saw some interesting books on soil science and analysis on Amazon.com. When I get far enough along with my current readings (other topics) I may have to purchase a couple.