Papery leaves Problem?

I have seen this problem a few times over the years, but this year about half my Phlox plants are affected.
The first, out of focus, photo shows how it first shows. The tips and sides of the plant leaf looses all its body. The end of the leaf is virtually transparent white, like a fine tissue paper. The second photo shows it progressing to fully damage the plant.
What is it, and how would I prevent/cure it ?
TIA

 

Difficult to say as this sort of thing happens now and again. I have in the past and probably in the future over watered a sick looking plant and made it worse. I have also tipped a plant out and inspected the roots, changed the soil/ compost and added more drainage and a little fertiliser.
Cut off the affected parts and re-pot worth a try.

 

This type of problem has been about over the past few years, ans without a closer look, it can be difficult, the papery effect can be caused by watering slashes, lack of nutrients, Phlox are prone to fungal infections too, and over crowding, leafhoppers etc transferes the problem quickly. But bybyour first picture my guess is phytoplasma, a pathogeon rife in Phlox, especially the Paniculata types, once its in, its hard to control, but splitting up clumps, regular feeding, givingbthem plenty or air, keeping on top of pests, and controlled water so as not to splash the leaves, dig them up, leave it a couple of years and try again.

 

@hans , @Cuttings thanks for the pointers.
I have repotted some of the sick looking ones, binning the really bad ones. They are in the GH in fresh compost and are lightly watered. I'll keep them on the dry side and see how it goes.

 

good show