I've had my Psychopsis for a few years now, and to be honest, it grows like a weed! It started out with 2 growths, and 2 spikes, and I now have seven spikes
I do fertilize every few waterings when I fertilize everything else. I have a few different kinds of fertilizer, and switch them around. I give lots of water when in active growth, and in a bloom cycle. Then let dry out a bit more between waterings in the winter.
I made a big mistake last year when I left it outside on my patio, and it got sunburned. I just cut off the burned part, and it seems to be fine now. I would say keep an eye out that they don't get more than an hour or two of direct morning light.
I repotted it one time into coconut husk chips, and I must of did it at just the right time, because there was no sulking which I heard they can do after repotting. Good luck with your new ones!