You don't mention where you live and what growing zone you are in which makes it difficult to make suggestions.
Lavender is a Mediterranean plant that likes excellent drainage and little or no water in the late spring and throughout the summer and fall.
The plant that appears to be dying may not be salvagable. You can try to move it to a sunny location. Dig the hole 6" deeper than normal and put in 6" of gravel. Do not plant the lavender any lower than it was in the original pot. Fill the hole with native soil mixed with 1/3 potting soil. Water it so the plant can settle in and then wait it out. It should not be in a place that gets watered by a sprinkler-too much water.
I'llhazard a guess on two plants that might do well where you had the lavender. they are aquilogia better known as columbine and heuchera better known as coral bells. Both have pretty flowers. Both take the shade.