Rootball is likely to be dry.

Can you deep water them? I use recycled plastic containers--gallon milk jugs--with a pinhole an inch from the bottom opposite the handle. Fill it with water and set it up close to the base of the plant. The water exits in a thin, gentle stream. When the water level drops below the pinhole, the remaining water keeps the container from blowing away/around with the wind.

transplant shock ...

use a stake and some string or tape.. to hold them up .. while the roots start pumping water again ...

you interfered with the roots ability to to pump enough water ... so the plants go limp in the heat of the day ... no matter how much water you provide ... but being rather large plants [presumption].. they cant lift themselves back up ... see link below for a discussion of such ..

two ways to avoid this ... smaller plants .. and planting earlier in spring.. when there is less heat ...

ken

http://forums.gardenweb.com/discussions/2000608/moving-a-large-fully-leafed-out-hosta-lots-o-pix?n=102

Liatris actually prefers poor soil over rich. If you move it to a sunny spot with terribly will your liatris will stand strong and tall. i hope this helps