Sorry I missed your post, it must have come at a busy period and then disappeared off the Active topics list before I got there.
Your wildflowers are remarkably robust, however if you are seeing them weaken it sounds encouraging. Enriching the soil is a help as they prefer poor soil. I wonder how deep their roots are, perhaps they grow like bindweed with long and deep roots. I am finding this year that my pink-flowered field bindweed is much weaker than last year, from removal using a trowel every five days or so, using a trowel.
Keep going and I hope you enjoy the books.