I know this is stressful, but hang in there!

Ok, lemme ask a question, just to verify, because it's a common mistake... you are not starting your day count until 24 hours after setting the eggs, right?? Day 1 doesn't actually start until 24 hours after set. I count the first 24 hours as day zero.
So, assuming the one really is on day 24, I sadly don't hold alot of hope for, but stranger things have happened. I think you just need to leave it, and see what happens.
The day 19 egg, I'm not sure i understand, but if you are still seeing veins, that's fine. If you don't see any, then it could still be ok, or it may have quit. If it is still alive, almost the entire egg should be dark. If you see much clear area, there are usually still veins present. But yes, silkies do have a tendency to hatch early, sometimes day 20. So it could be getting close.
What did you see?