I don't think there's any problem with the medium. Altough old, it has been accomplish its main function while keeping a more than good drainage.
I remeMber reading (and now I've found it again
) that an increase in anthocyanin may happen when there's a magnesium deficiency (see here on "
Magnesium Deficiency"). That's a possibility as I've been watering it a lot less because cold temps and water are not not compatible for anceps and the drainage is so good that a lot of the water falls on the neighbor's balcony. So, to avoid any problems.....
Just for educational purposes I'm tempted to leave where it is and water with Epson salts but I won't do it as temps are too low and I don't want to stress the plant. I'll move it indoors for a few hours and increase the magnesium.
When all the 7 spikes have bloomed, I will post some photos and an update.