Iconian, Krynn, Torian:
Cheap techs don't usually follow after an expensive tech, so it is odd that you research Enhanced Adaptation/Interstellar Expansion for 10 or so turns, just to research Xeno Biology in 1-2. Pop Growth is very important and should not be delayed by an expensive tech like EA/IE. I would be best to reduce cost of these techs back to vanilla. So:
Enhanced Adaptation/Interstellar Expansion cost from 600 to 150, back to vanilla value. Bonus from 10% to 5% for Torian, 8% for Krynn, and 8% for Iconian. Planet Quality works regardless of how much of it there is, so with 5%, Torian can increase >20 PQ world by +1, and Krynn/Iconian can increase PQ >13 worlds by +1. While not as strong, it is still working and stacks with colonization events. Changing it will not only make it just like in vanilla, it is also a really small nerf to greatly performing Torian, Iconian and Krynn. And disproportion of tech costs will be less noticeable.
I think Space Mining should be unlocked by same tech as other races, especially since all 3 races do not lack this tech (currently logistics). Making your planets more hospitable has not a lot in common with mining in space ^^.
Krynn description: Now that everyone has new/improved/longer descriptions, theirs is just... well... vague? I never play them so no propositions from me.
Their tech tree looks ok and can stay, with exception of Space Mining - while it is still kind of Geology field, their tech says nothing about geology in space, only on the worlds they inhabit.
Now that they get +1 speed, their research should be reduced back to 25 (vanilla) from 35. They were underperfoming because of the lack of labs and overbuying things, like Maiden wrote, not because they are weak. They even get easy +25 Social Production, so lack of bonuses is definitely not where their problem lies.
Now that they get speed bonus akin to vanilla, Military Producion could be reduced to 0/5/10 (0 in vanilla). This would make them even more different then Korath.
In case of the Yor this could be a bit of the a problem since they get morale from this tech but they seem to be doing just fine.
Drengin and Korath will be impacted by this change more. They get not only morale, but also pop growth from their last tech. They should get it early, otherwise pop growth bonus is wasted.
Because their labs have lower output per tier (just like in vanilla), they are not able to get so much research of one planet as other races. In essence, they need more planets to achieve same research if we include same tier of labs. They are unable to match research of others, and even if AIP7 wasn't broken, this still would be the case, only on a smaller scale. They are militaristic and spend loads of money on military (production and maintenance), and because of their ethics they are constantly at war. They need to get higher level of labs earlier, as both Drengin and Korath are a "rush" civs. The research cost of their labs should be lowered even more to vanilla values. While I think in vanilla they may have been too cheap, I believe in CU they are still a bit too expensive, even after recent reduction. Vanilla/CU/New proposal
Diabolical Research 100/200/100
Imaginative Research 400/700/500
Ultimate Diabolical Research 1200/1800/1600
Pain Amplification 800/1500/1200
So altogether around 30-35% more expensive then vanilla. This will enable them to get better in research, at least until others get Discovery Sphere.
Korath description: "plunged the the Drengin..."
Yor get Terror Drones. Cost 250. 20% max/min bonus to attack. 25% imp. damange. No randomness, Yor style.
-Thalan get Mechanized warriors. Cost 250. 50/90% bonus to attack. 100% imp. damange. This attack is slightly more powerful than Shock Troops but much more expensive and desctructive. Simply put, I don't want Thalan players capturing intact structures. They're super hivers, they can rebuild planets like it's no one's business. The Thalan have "expensive technologies" hence the high cost.
Let me stress that again
all other civs get free +30/30 attackers advantage on Space Marines. Hence to keep the balance right, both Yor and Thalan need to get an equivalent of invasion with 30% to attackers advantage for 0 bc.
While Mechanized Warriors has good % attack bonus (40-50%, taken from xml), its cost is horrifyingly high, especially when you consider destruction of improvements. I suggest lowering the cost to 400 bc from 800 bc, so it is cheaper then Space Marines, but is weaker then Shock Troops and leave you with no captured structures at the same time. Unless it is just a typo, and you planned to give them stats of 800bc +50-90% attack with 80-100% improvement damage, in that case it is balanced - they get better invasion capabilities then 30% for high cost.
Thalan description: Last sentence is long, could use a comma somewhere.
Terror Drones cost of 250 bc for 20% attackers advantage is also not appropriate. Again, in vanilla Mini-Soldiers cost 500 for 40-70%, and now this tech renamed Space Marines still cost 500, but for 70-100%. This is 30% increase, so Yor need to get at least 30% invasion tech to compensate, not 20%. Cost should also be lowered at least to 200. They do get No Mercy Invasion Center, so in later stages cost is not relevant, but a GA should be something that gives you a boost, not something that moves bad/overpriced stuff into usable section On the side note I would like to see this improvement back at Concept of Evil or even a tech branching of CoE, but only for Korath/Drengin/Yor/Korx - same as Good races and their PQ/Creavity tech.
Yor description: "Cold an calculating and bereft of emotion..." - too many "and", could also use less adjectives. Cold, calculating and merciless already encompasses lack of emotion.
Loyalty doesn't do much for them. High pop growth (Breeder), high pop cap (Harvester on every planet) and cheap +influence structure (Temple of Memories) renders their worlds almost immune to rebellion. What they could use, is 5-10% more pop growth to help them more if they don't keep approval at 100%, and maybe 10 Defenses (they should have some experience by now).