Stapelia cuttings not growing

[cwatson1414]

Hey TF. In November or December I picked up some Stapelia leendertziae rooted starts. They grow under 4 2' T5HO lights. Temps are moderately warm. My other stapeliads are growing. They have rooted into the media, and they have been accepting water for several months. They have not, however, put on any new growth.
I'm not sure what the issue is. There are two stems. One appeared to have suffered cold damage in transit, but appears to have recovered (It had a white-flecked-with-purple splotch which has gone back to green.)

Any advice is appreciated. Thanks TF!

 

[DragonsEye]

Some plants do seem to have a definite growing season though whether this is the case for this species I do not know.

May simply be a issue of timing but perhaps this summer putting it outside would provide a stimulus?