Hello friend. For a healthy hedge a fertilizer with a 3:1:2 or 3:1:1 ratio (N-P-K) like 18-6-12, 24-8-16 or 18-5-9 is generally recommended because of the need for more nitrogen. Hedges are mostly foliage plants with most of its production centered on foliage. The first number should be higher than the others.
Nitrogen is a vital component of chlorophyll, the pigment that allows plants to capture sunlight and convert it into energy through photosynthesis. It's what makes leaves green. Be sure its slow release so you don't burn your plants.
I would cultivate the soil around the base of each plant and top dress with a tiny amount of fertilizer to the top inch of the soil. It would be best to have a soil test before dumping fertilizer on any plant.