Be sure you didn't plant too deeply. Check the crowns for rot. Dormant, still pushing roots is ok, but check to be sure.

Mid spring, early summer is fine for dividing Carex testacea, so you should be alright there.

Thanks Grass Guy. When Will I know for sure? Is it a later perennial grass? Does it need really warm, sunny days to get going? Grasses at front of border seem to be growing faster. Although all of these get full sun.

maybe someone from zn 6 can chime in that has carex testacea growing. I would think it would be warm enough for it to be pushing even from divided clumps. Did you have a bad late cold after dividing?

For future reference, Do I need to divide these frequently or prune them in the spring. Thanks.

Trim if needed, but don't cut these back hard. They usually are fine with just a cleaning, rake through the foliage.

I'd divide the larger clumps in late spring, maybe even early summer when they are really actively growing. I shouldn't have confused it by saying 'dormant' is ok. They aren't going to go true dormant for you - they are evergreen, but won't be actively growing in your cold winter - as evergreen as copper sedges can be :). If you had a really cold winter, it's possible you may have lost some of the grasses. Or if they were cut back hard when divided, they may not have liked it.