flaming katies

i've had two of these for about six months, bought as house plants - one with red flowers, one with pink. they've lived side by side throughout, indoors, by a north facing window - i understand they don't like it too sunny. the red one continues to flourish, the pink one is flagging fast. the flowers have mainly gone, and the leaves have wilted/turned brown. any idea why this may be? perhaps the red one is just a more robust strain?

also, is it a foolish idea to think about replanting these outside?

 

cgbg, Kalanchoes DO like the sun, not necassarily all day but at least somewhere bright. North facing windows are not ideal. Have they been wet fora long time? this is a common cause of withering and collapse.
They are both strains of the Blossfeldiana species so should have the same robustness.
Planting them outside may not be a good idea especially if the ground remains wet for a time as they need good drainage .