Have you used Ctrl-N, and are the intelligences of the slow races listed correctly in the foreign policy screen? Most of TA's AI work happened during April, so they should be quite a bit stronger than when the OP was made.

All the AIs are set on Bright, Yor included. Haven't used Ctrl-N. The Yor don't seem to lack for colony ships, but they aren't keen on sending them anywhere. It should be especially noted that even though they can colonise Barren worlds without needing to do any research, in this game they failed to snag any of the ones that were nearby. Feeling sorry for them, I ended up just giving the Yor a couple of planets that aren't of any consequence. I think the Torians will wipe the floor with them though.

As I said, on a lower difficulty setting (again with all the AIs set the same) the Yor managed to expand without too much difficulty. Maybe there's nothing to that, but since the algorithms do change between the two levels of difficulty (or so the description of the difficulty settings reads) it's possible that the less intelligent algorithm is working better.

I guess that starting a new game with all the same settings might help to determine whether they just had a bad start. After all, they were basically thrown in the same quadrant as me.

I have noticed this exact complaint on suicidal. They hoard colony ships and don't send them out. I have most of the AI sitting there retarded. I buffed the Yor myself with some modifications and replaced the drath with a new race that is programed to perform well (honestly all they need is an increase to racial pop growth bonuses to be successful) I took out the terrans who were perfoming well and made a new bonus set up for them as well as another yor like race. The torians do well but that is all.