This is a common problem in my old neighborhood. The builder apparently got a batch of red oaks from east tx or somewhere with acidic soil. They've been yellowing and many have died the past few years.

Unless these are really large trees, I'd cut my losses and replace them with something more suited to our alkaline soils. Sure, the implant may work, but on the other hand, you may just be prolonging the inevitable.

My $.02.

You would really need to acidify the soil so that the tree can use the iron that is probably already in the soil but insoluble. Iron becomes unavailable to plants in alkaline soil (it's a chemistry thing). Since tree roots travel a great distance you would have to acidify a large area which would be prohibitive costwise. I agree with bjb that your best solution would be to replace the tree with something native or adapted to alkaline soils.