In short, Spawn #29 was not pulled on Monday, the 14th, as I had initially suspected.  Looking at it, I opted to wait until Tuedsay, the 15th, to pull it, 7th day post spawn.  I used well-aged new saltwater which was 1.026; same as the broodstock water.  Water temp may have been a couple degrees cooler.  The eggs were given a H2O2 bath for roughly 15 minutes (4 ml to 0.5 gallons saltwater), and then placed in the 10 gallon hatching tank with a wooden airstone.
Come Wed. morning, there had been minimal hatch, most eggs were on the tile and still looked viable.  I saw only one larvae swimming.  I opted to do nothing, and let it go another day.  Come Thursday morning, once again, no eggs on the ground really, some dead larvae, and one viable offspring. Eggs were all dead come this evening.
I’ve noted repeatedly over the years that despite what everyone says about using ‘new saltwater’ for hatching and incubation, I NEVER have good look with it.  Was it the temp drop in this case?  Possible.  But every time I use broodstock water, I don’t feel like I have these problems :/