Here's a bit more for the timeline ...
June 2
2012 hrs - second chick hatches
June 3
just prior to 0500 hrs - third chick hatches (looked " hatch damp" at 0500)
0500 hrs - first meal on camera
0623 hrs - second meal on camera
Went through the recordings since first hatch and it does look like one of the chicks has died. From just before 0500 hrs when there was enough light for one of the cams to see the box, there have been 2 active chicks, 1 motionless chick and 1 egg. Could have been just hours old chick exhausted from hatching but I'm inclined not to think so. Would be happy to be wrong however ...
Not that it matters and there really is no way to be sure, but I'm inclined to think it was the third chick to hatch rather than the first or second based on size and from watching this morning's meals. One of the surviving chicks has more control than the other which would indicate it is older than the other. Given that there is a 14 hour gap between chick 1 and chick 2, that could account for it. The gap between chick 2 and chick 3 is about 6 hours and given that it was night time, not sure I would expect to see that much of a difference between the two. Could it have been chick 1 and chick 3? It could but the motionless chick looks smaller, I haven't seen it move at all and it looked a bit damp when I got a better look at it at the second mealtime and at latest shift change the adults are still brooding it and it looks fluffy white and dry like its sibs.