Vinca tend to do poorly with too much water, they seem to rot out at even the thought of being over-watered. Where are you located? If you're in a colder zone it's still a bit too early for vinca in the ground (zone 5, anyway) -- vinca HATE cool/cold soil, and too much moisture makes the situation worse. Pictures would help, though.

i hope you didnt spray in afternoon sun ...

i would not water in the afternoon ... IF i had to wet the leaves ...

dish soap is often a detergent which is not great to spray on tender leaves ...

how about a pic or 2 ... hard to speculate without such

have you dug any up.. and actually looked at the roots??? .. might be a good place to start ...

ken

Pictures would be very helpful. And do you mean Vinca species or Catharanthus?

All, first thank you very much for the replies. Attached are the pictures of leaf wilt. The first picture shows the beginning stages of leaf wilt. The second picture shows the extent of leaf wilt.

@Ken if I were to dig out a plant what should I be looking for when observing the roots?

@rhizo_1 I had bought these from Lowe's. The label says Catharanthus roseus.