I remember reading somewhere that orgainc fertilizer tends not to give much early season results due to the cold. Liquid fertilizer was recommended for early season fertilization because it is more easily utilized by the plant in cold weather. Of course, you need to be sure that you do not push too much growth too early. I have not fertilized yet this year in the Charlotte NC region, and I would suspect that we are a little ahead of St. Louis warmth-wise. I use miracle-gro for everything. If you fertilized well last year, you may just need to wait for new growth to emerge.
Post a picture of one of them, it will help all to see what the trees look like and offer better advice.
Finally, I might check for spider mites, they tend to wash out the color on shimpaku, which they seem to like more than any other juniper in my yard. I have problems with them here even in winter, they never really go dormant, and can even multiply during our winters.