Hi James, thanks for the question.

Nutrient issues are not the easiest to figure out. Ratios of nutrients can be as important as the level.  The test recommendation is bringing potassium more in line with the other nutrients.  Stunted growth can be caused by nitrogen and potassium deficiency.  Both these nutrients can easily leach from the soil.  If you have sandy soil you may need to fertilize less but more often. Weather this year has not been friendly to growing. either.  This can affect the growth.   Air and soil temperatures, rain, lack of rain, winds can affect the growth of the plant.  Germination can be a result of out-of-range soil temperatures or a water issue.  Old seed can also be a factor here.

Check out the following links:

Making the most out of your soil test - MSU Extension

Poor Germination of Vegetable Seeds | University of Maryland Extension (umd.edu)

I hope this helps.