Possibly T. festucoides or T. juncea.

T. setacea

gotta give Gonzer A+ this 1's T Setacea
cliff

I bet "festucoides" is the real name of what was sold to me as "grassifolia". My plant is shorter than yours, but may be younger. It's easy to separate young plants off the main plant, and mine all seem happy. I think they chat with the juncea, which may be distant cousins.

'Grassifolia' is just a random name picked from a hat for sales purposes.

Thanks for the IDing, folks! Some of these look so much alike to me (like my #3 which apparently has several options), that I'd be at a loss in many case even to narrow down the playing field.

Bartramii

It is not T. bartramii.