I tried posting this over the weekend, but my post got eaten by something and I was too tired to do it all again.
The babies died. All of them. I knew the little one was going to die. It passed the day after the fall. Then the second one was almost dead the last time I saw it. The next morning they had disappeared. I'm not sure if the mom got rid of them or something came and ate them or what. The strongest of the babies was still in the nest which is why I'm thinking it must have been mom who did it. The last baby died by day 3.
I'm not sure why, but I believe the mom (or dad, you can't tell male/female titmice apart) gave up on the babies. The feedings were few and far inbetween. I watched for 20 minutes straight at one point and never saw them fed. I wonder if the fact that only one parent was doing the work was what made the difference. The last time we helped out a fallen baby, there was only one baby and 2 parents. Maybe 3 against 1 was just too much.
So nature has taken its course, sadly. One positive note is that within that time, I saw another Titmouse parent teaching it's young one to eat at the feeders, so we'll have plenty of future Titmice around.