Wilted leaves on phlox
Can you please tell me what is causing the leaves on my Phlox to wilt? They are wilted clear up to the flowers. And the plants aren't next to each other, ie: the 1st one will be so and then the 3rd or 4th one will be the one around the corner the 6 or 7th one will be. There is no rhyme nor reason as to which one is wilting. There is no sign of the white powder on them either. Some are very old plants. Thanks for your help.