Hello again, and update:
It has been 6-7 weeks since the baby shrimps were born. Ever since my last post, things were going ok. Some other shrimp keeper advised me to keep the water changes down to 10% every 1-2 weeks. I counted a maximum of 17 shrimp babies 3 days ago, so I don't think any were lost in those two weeks . Two days ago, I put in a small amount (1/5th of a dose) of Dr Tim's Waste Away, one of those products that claims to have bacteria that eat away waste. But then over the next two days, I've lost 3 or more babies suddenly. I usually find them on their side barely moving, with nothing obviously wrong with the body or color, and the only slightly odd thing is that they have their swimmerettes sticking straight out instead of folded up like usual. Most of the adult shrimp are ok, many babies are actively grazing away, and some of the babies are very quiet (could also be pre or post molt).
Well, anyways, I blame that bacterial product for now, because there isn't anything else that I did out of the ordinary. The feeding schedule alternates between boiled spinach, mulberry pellet, shrimp food pellet, and Bacter AE. Perhaps I've feed too many days in a row without a "rest day"? (ammonia, nitrite and nitrate still read zero)
Any ideas what could be wrong, and how to recover?