Q.wave petunia
I have 2 nice large containers of wave petunias.
They sit on my patio which is on the west side of my apartment building.
They get full sun only in the afternoon and evening.
Is this not the best for the wave petunia?
When I bought them they were full plants with a lot of flowers.
Now they are drooping and do not look the best.
I do keep they watered.

Full sun with evenly moist soil is ideal.
Containers will need daily water and even twice a day when the temperatures are above 80 degrees.
Here is a link to refresh you on the care requirements.
https://www.gardeningknowhow.com/ornamental/flowers/petunia/wave-petunia-plants.htm