What you want more than a difference from day/night temp is overall lower temps. However, even so some will bloom without that. Yours look pretty healthy, so that's a plus. They could probably use a little more light, if the color is coming across right on my computer. Can you add a plant light on them when the sun isn't?

As for the little purple thing (which I can see!) its too soon to know if its a root or a spike, sorry! Get another picture as it grows, a root will be pointy, a spike will have a tiny lump on the end, to turn into buds. Good luck!