Petunias die very easily. However you can try to revive them by cutting back any yellowing foilage, submerging the plant in water and then placing in a shady area. Keep an eye on the plant and keep the soil damp to see if you can save the plant. Adding a fertiliser may also help revive the plant.
First cut back the yellowing leaves, then dunk the plant in water. After the bath, place it in a shady area. Add some fertiliser to the plant, and then keep a close eye on the soil. Keep it damp and hope the plant comes back.
Petunias are hearty and can survive the neglect but it may take several thorough waterings. Thoroughly water the plant and allow thirty to forty minutes in between waterings. If they don't return to full lushness, try pruning one of the plants all the way back. They revive quicker and fuller when the they aren't lanky.
