I may be wrong here, but I think that wildflowers don't need any extra fertilizer. I think you should be fine. :-)

"One man's wildflower is another man's weed", and like weeds, and most "wild flowers" by definition need very little in the way of help from us. Most actually do better on marginal soil. I mean, if they needed cultivation, they wouldn't be wildflowers. Fertilize if you want, but it will probably just incite less desirable "wildflowers" to grow and compete with what you're planting.

Thanks for the info, all. :-)