The most likely possibilities at this early stage are:
Injury or stress during transfer
Too many rotifers, which decrease oxygen availability in the tank
Thin larvae (insufficient yolk sac) which can be parent nutrition or a hatch delay that causes them to use up some yolk before they hatch. Thin larvae can usually last into the 2nd day, though and if you see any yolk left at all they hadn't starved yet. What did the yolk sac look like on the ones that died?
Water conditions could do it, but it sounds like you're on top of that. I wouldn't have done any water change yet this first day, but that's not a big deal given your timing.
If you think the larvae left are thinner than they should be, leave the lights on longer or even over night to keep them feeding. You'll have to add rotifers more often to keep you density up.
What about the rotifer tank? Is there any ammonia or pollution making it from the rotifer tank to the larvae tank? You're straining the rotifers that you add, right? Not adding rotifer tank water to the larvae tank?
I'm really reaching here .... trying to think of any remote possibility.
We already talked about having enough, but not too much air.
How are your first two doing? Any color change yet?