The crested one looks like a leninghausii indeed. Since I can't post links yet, I pulled this picture of a crested leninghausii off the web:
I was worried that the yellowing is due to some mistake I made. I have two of the species pictured in the fourth photo. They both were completely green at first. Now one is green and the other isn't. The same goes with the other Parodia, which now has a nice gold-ish hue on top.
The one with the four arms lookes like a leninghuasii, but I wasn't able to find a picture of that species with arms online. Hmmm...
