My guess is something cut the stem.

Definitely not broken stems, this entire shrub is wilted

Did something eat the roots?

Rekha,

I agree with Librarian, my first thought was something is wrong at the root level.

looks like black marks at the base. Could be fungal infection got in through a wound. Although that usually shows up in hotter weather.

You really need to dig the plant up to do an autopsy.

Tried to pull it out, did not come up. I have to dig it up, it chilly here, so will do it in a couple days. To be clear, some of them in the same row are perfectly fine, and some have this issue...