Even with 100 degree heat, watered nightly? That sounds like too much water especially if a mix of clay and potting soil. Many lavenders have been killed with too much kindness and water.

Plus did you give the plants a chance to acclimate before putting them in the ground? Nursery plants are sheltered and pampered things and when you bring them home it is usually best to keep them in a somewhat sheltered location for a few days until they have a chance to get used to your conditions.

FataMorgana

Hmmm...so I'm watering it too much. I did leave it in it's original pot placed in the location I was putting it for a few days until I got around to planting it (6 months pregnant and very hot outside,lol) so I think I did that part right atleast. The problem is that it is in a location with other plants that need to be watered daily. Should I put it in a pot for a while? It's been in the ground for about 3 weeks now or do you think that will do more damage? Thank you for your help, knock on wood this is the only plant I'm having a problem with right now.

Does the entire bed have potting soil mixed into it or only the planting hole? If it is just the planting hole you may have created a bathtub effect and actually hurt the drainage. It's better to plant the new transplant in only the soil it will be growing in.