Rose of Sharon
The shrubs are in their third season. This year two of 4 are not blooming or ha e very , very little bloom or leaves. The other two are fine the growing conditions are the same. Full sun in a burm.
Some varieties may be a little less tolerant of full sun, but this will not usually hurt the blooming process. It can be attributed to nutrient deficiencies, or moisture issues if water collects in the area. This article will help you start determining what could be the problem: https://www.gardeningknowhow.com/ornamental/shrubs/rose-of-sharon/rose-of-sharon-not-blooming.htm