Well damn. I stripped it down and immediately noticed chunks of rubber laying around the spring for cylinder #1. I pulled the spring and found this...
In case you can't see it, the umbrella seal is shredded. I can push the "mouth" of the seal over the guide if I want too, but it doesn't seem to fit as though it was meant to. If I do that, the inner spring on my valve springs seems to rub against the seal (which is why I didn't put them over the guide in the first place). Perhaps they were shredded because they were loose on the stems?
I have all 12 o-rings but no other umbrella seals. The springs I'm using are the ones from 12bolt.com and I'm nervous they'll touch anything fitted over the guides.