Most landscape trees in Michigan will not require much, if any, fertilization for good growth and color. If the trees appear healthy, you can forgo fertilizing in general, unless you are trying to push growth for something like a windbreak or for use as Christmas trees. In either case, wait until the second year after transplanting to fertilize. Since you planted this spring, wait until spring of 2025 to fertilize with a high nitrogen fertilizer. 

There is a nuance to this. If you decide to fertilize, apply organic nitrogen sources in the fall after bud set (that would be fall 2024), or inorganic sources in the spring, about the time growth resumes (spring 2025). This is because organic sources release very slowly over time, making fall application ideal so nutrients are available come spring. 

Keep an eye out for needle loss beginning in the lower branches of the tree and progressing upward. Blue spruce trees are highly susceptible to needle cast diseases and decline when grown in Michigan.

If you have not done a soil test, it would provide useful information on your soil pH (acid for pine family) and any nutrients that may be lacking in the soil: 

For more information:

https://www.canr.msu.edu/news/soil-testing-returns-through-msu-extension

https://www.canr.msu.edu/uploads/files/Nutrition_and_fertilization_BertCreggfinal.pdf

https://www.canr.msu.edu/resources/christmas-tree-planting-guide#skipfertilizer

https://www.canr.msu.edu/resources/alternative-conifers-for-michigan-landscapes

The photos came through low resolution, so I cannot get a good look at the trees. However, the ones that appear "thin" do not appear to be adjusting well to the planting site. This may result from transplant shock, improper planting, or stressful growing conditions (e.g., too wet, too dry). I'm not at all convinced that lack of nutrients is the problem, so I would not expect fertilizer to fix the issue. That said, aged manure can be applied in the spring around the time new growth resumes, and I have included a link to an article on that below, as well as information on dealing with problems in blue spruce trees. As mentioned previously, blue spruce trees are performing poorly throughout Michigan, and may require considerable work to keep healthy and beautiful. If you have not done a soil test, I would still recommend getting one. High soil pH in particular can be a problem.

https://www.canr.msu.edu/news/help-me-save-my-blue-spruce

https://hort.extension.wisc.edu/articles/using-manure-in-the-home-garden/

https://www.canr.msu.edu/news/soil-testing-returns-through-msu-extension