For me I let go it down in the starting of fall like it is, sometimes 5C at day and night. then I turn on the heating in the hole house.
After that tmep will not go under 10C maybe 8C at night.
Normlay as it is my office, I have it around 15C when I am in but not over 20C in winter time.
Sometimes I make it higher when I am cold so I think this stimulate them and is the same in nature. But dont forget after all they like sun a lot. Mine stay in the first row of the window, the once more behind never flowered.
Micranthum is the last row and emersonii.
Delenatii like the high light too but need even less water then armeniacum.
All depending my condition and my feeling.
By the way K-lite dont liked by armeniacum and micranthum, since I went back on my old fertilizer, chep one with cheap nitrogen source they speeded up again in growing.