does one side get more afternoon sune than the other? i had this problem, i’m in NC and the ones that got the more intense afternoon sun wilted. also something my grandmother always told me was not to water outside plants in the afternoon or evening to water them of the morning when it is not as hot, she always said it would burn them. not sure why.

something is wrong with your soil or you have a critter or disease killing the roots.
Do you have a dog. Dog urine kills plants quickly. I’ll bet cat urine is just as bad. Smell the plant. If it smells of urine then that is the problem. Or, you could pull up the dying plants and inspect the roots. If the roots are gone or look nasty then take them to a nursery and see if someone there knows what is going on.

I don’t know. Is the soil the same? Is there an animal fertilizing it or spraying it? Somethings are just unexplainable. I wish I could help!