Around day 48, the die-off was getting pretty frustrating. I made a few observations:
1) Clutch 2 was quickly catching up in size to clutch 1, highlighting the fact that growth had slowed down considerable with clutch 1.
2) It appeared that clutch 1 was eating up all the frozen bbs in the feedings, but leaving most of the cyclopeeze.
This lead me to the hypothesis that perhaps the frozen BBS was not nutritious enough for them. I considered 4 options:
1) Continue down the course I was taking and see what happens.
2) Eliminate the frozen BBS from the diet to force them to turn to the more nutricious cyclopeeze.
3) Try to move them to a different frozen food.
4) Supplement there feedings with live BBS
I decided to go with option 4, and have been including newly hatched BBS in the first and last feedings of the day. I had 2 more die about a day after re-introducing the live BBS, but have not lost any more in the 2 weeks since then. In all, I lost 16 between days 36 and day 49, but still have 24 going strong at 63dps. My plan at this point is to stay the course with supplemental feedings of live BBS until they get bigger and look like they are eating the cyclopeeze.
Clutch 2 is now 35 dps, still on 100% live BBS, and has experienced no losses (41 alive).
I kept the male separated for feedings for about 10 days before returning him to the broodstock tank. There have been no spawning since then, but he is eating like crazy.