Once soil is dry enough, slip the rootball out and check the roots for white growing tips. If they are dark brown or black...damage from the cold has likely been done. (a root trim and re-veg might be advised)

Do not overstress them with additional nutrients, additives and foliar sprays. That stuff doesn't regenerate neckrotic cells, and will compound your problems.

Old growth is old news...is there any new growth at all?

Only bad things happen overnight. Have patience with their recovery. (but keep an eye on 'em)